Friday, 1 May 2015

T-72: Part 1



The T-72 is known as one of the most numerous tanks in the world today, and the tank is likely to remain in some form of service for the rest of the 21st Century, so before we examine the history of the T-72, let us see how many of these tanks were actually built. A few years ago, Uralvagonzavod (UVZ) made efforts to declassify much of the history of the T-72 tank, including the number of tanks built by the factory. The table below was from the factory archives of the UVZ, published in the book "T-72/T-90: The Experience of Creating Domestic Main Battle Tanks" by the Nizhny Tagil factory, authored by S. Ustmantsev and D. Komalkov (head designer of the UVZ transport engineering bureau).





From 1973 to 1990, 18373 T-72 tanks and T-72 derivatives were manufactured at the UVZ factory floor, and another 1600 tanks were manufactured from 1991 to 1996. The Chelyabinsk Tractor Factory also took part in the manufacture of the T-72 tank, producing 1894 tanks themselves between 1978 and 1990. In total, 20267 T-72 tanks were produced in Soviet Russia, making it the second most numerous tank ever produced in both the USSR and the world. But how did it come about? The 2010 book "T-72 Ural armor against NATO" by noted military historian Mikhail Baryatinsky details the history of the development of the tank, and is the source for many of the diagrams and pictures shared below.

Firstly, it should be clear that the T-72 is indeed a "mobilization model" with slightly inferior performance compared to the T-64. Some Internet sleuths found this chart of prices showing that the T-72A (1979) was significantly more expensive than the T-64A (1968), but despite this, the fact remains that the T-72 was created primarily because the Kharkov design bureau responsible for the T-64 was too busy with the T-64 itself to be concerned with designing a simplified version of it - a mobilization model, in other words. The technology of the T-72 Ural was also very conspicuously inferior to the T-64A in major ways. The more expensive pricing of the T-72 does not change the fact that it is a less sophisticated product compared to the T-64.

Moving on, let us take a look at the Object 167. It is a precursor to the T-72, but is better described as a T-62 taken to the extreme.




The Object 167M had an early form of the now-famous AZ carousel autoloader, composite armour for the upper glacis and turret, a 125mm D-81T cannon, a V-26 engine which developed 700 HP, a reinforced transmission to deal with the increased power, hydraulically powered gear shifting systems, new "Liveni" two-plane stabilizer system, and a new suspension composed of six roadwheels and three return rollers. The tank did not enter mass production because the T-64 had already been ordered to enter production by a resolution from the Council of Ministers of the USSR, but this was definitely for the best, since the Object 167M had numerous drawbacks of its own. In February 26, 1964, the scientific-technical council GKOT examined the Object 167M project and rejected it. This was the end of the road for the Object 167, but it was destined to leave its mark on Soviet tank history, as we shall see later on.

Vitaly Kuzmin has good photos of the Object 167 when it was exhibited at Patriot Park 2015. Click here to view the photos on his website.


On 5 January, 1968, the Minister of Defence Industry S.A Zverev gave the order to begin the "modernization" of the T-64A by the Uralvagonzavod design bureau in Nizhniy Tagil after some persuasion by Leonid Kartsev on the advantages of replacing the basket-type autoloader in the T-64A with the carousel autoloader developed by UVZ, and also on the replacement of the 5TDF engine on the T-64A with a supercharged derivative of the V-2 engine (from the T-34) developed in Chelyabinsk. The minister was impressed by the autoloader and was enthusiastic on the idea of putting it in the T-64, but he only caved in and agreed to also changing the engine after Kartsev's persistent attempts to sway him. As part of the programme, six T-64A tanks were sent to UVZ. For the next few years, all prototypes of Kartsev's new tanks would either be modifications of these six T-64A tanks or modified copies thereof.

The first of these modifications, dubbed "Object 172", was completed in the summer of 1968, and the second was completed in September of that same year. The Object 172 differed from the T-64A only in the fighting compartment, which had to be rearranged to fit the new autoloader, and in the engine compartment, which was completely reworked for the V-45K engine and T-54-style cooling system. 
Because most of the modifications were internal, the Object 172 was practically indistinguishable from a typical T-64A from the front, but the rear of the turret had to be modified for the autoloader's ramming and ejection system, while the engine compartment had to be lengthened to accommodate the new powertrain and cooling system. The left side of the hull gained an exhaust port just above the second rearmost roadwheel - a location reminiscent of the earlier T-54 and T-62.





Baryatinsky's book gives us the details of the late stages of gestation of the T-72. Here are a few translated paragraphs:

"Then in the Design Bureau of the UVZ, which since August 1969 was headed by V.N. Venediktov, it was decided to use the chassis of the Object 167 with rubberized roadwheels of increased diameter and more durable tracks with open metal track pins similar to those of the T-62 tank. The development of this tank was carried out under the designation "Object 172M". The engine, boosted to 780 hp, received the index of V-46. A two-stage air-cleaning cassette system was introduced, similar to that used on the T-62 tank. The weight of the Object 172M increased to 41 tons, but the mobility characteristics remained at the same level (author's note: same level as the Obj. 172) due to the increase in engine power by 80 hp, the capacity of fuel tanks by 100 liters and the width of the track by 40 mm.


From November 1970 to April 1971, Object 172M passed a full cycle of factory tests and then on May 6, 1971, was presented to the defense ministers A.A. Grechko and the defense industry SA. Zverev. By the beginning of the summer, an installation lot was set up from 15 vehicles, which, together with the T-64A and T-80 tanks, passed many months of unprecedented scale. At the suggestion of Major-General Yuri M. Potapov, a battalion composed of platoons of three companies was formed. At the same time, each company was manned by tanks of the same type. The route of the traffic was chosen from Dnepropetrovsk through Ukraine to Belorussia to Slutsk and then back to Dnepropetrovsk, and then through the Donbass and the North Caucasus to Baku, across the sea by ferry to Krasnovodsk, through the Karakum desert and the Kopetdag mountain range. The tests were due to be completed at a range of 60 km from Ashgabat. During the march, live firing tests were conducted at various firing range, and platoon and company level exercises with live firing and driving were carried out at various tankodroms (training grounds).

After the end of the tests, a report with the title "Report on the results of military trials of 15 tanks 172M, manufactured by Uralvagonzavod in 1972." was submitted. The final part of the report contained these remarks:

  1. Tanks have passed the tests, but the lifespan of the tracks of 4,500 - 5,000 km is insufficient and does not fulfill the requirement for tank travelling capability of a distance of 6500 - 7000 km without replacement of tracks.
  2. Tank 172M (warranty period - 3000 km) and engine V-46 (350 m / h (?)) worked reliably. In the course of further testing up to 10,000 - 11,000 km, most of the units and assemblies, including the V-46 engine, operated reliably, but a number of major units and assemblies showed insufficient lifespan and reliability.
  3. The tank is recommended for adoption into the armed services and serial production, provided that the identified shortcomings are eliminated and the effectiveness of their elimination is checked before serial production. The scope and time frames for improvements and inspections should be agreed between the Ministry of Defense and the Ministry of Defense Industry.


In accordance with the decision of the Central Committee of the CPSU and the Council of Ministers of the USSR of August 7, 1973, Object 172M was adopted by the Soviet Army under the name of T-72 "Ural". The official order of the Minister of Defense of the USSR was published on August 13, 1973. In the same year, an pilot batch of 30 tanks was produced at Uralvagonzavod."

And thus, the T-72 was born. An amalgamation of the T-64A and the Object 167, the T-72 would go on to become the second most widely produced tank in the world, behind only the T-54.





In the end, the T-72 turned out to be so similar to the T-64 that you could not easily tell them apart, yet different enough that there was minimal parts commonality between them. This was one of the many headaches caused by the rivalries in the Soviet tank building industry, but this does not change the fact that the T-72 was an extremely capable tank.

But before we take a look at the T-72 in earnest, we must first remember that the original Ural variant underwent several major upgrades throughout its lifetime, creating significant discrepancies between each successive model, and to complicate matters, each model in itself may have subtle improvements implemented during overhauls. Without going into very much detail, we can condense the evolution of the T-72 tank into a few main models. Some of the information below comes from the Russian military historian A.V Karpenko, but there are many other details that cannot be e.


Object. 172M (T-72 Ural) 1973-1974

The original T-72 model, with the simple pure cast steel turret and optical coincidence rangefinder-based sighting system. The IR spotlight was originally located on the left side of the cannon like the T-64A, but it was relocated to the right side in 1974.


Object. 172M1 (T-72 Ural-1) 1975-1979

In this model, the "Gill" armour panels on the side of the hull from the T-72 Ural (originally from the T-64) were replaced with conventional side skirts sometime in the middle of the production run. The optical coincidence rangefinder-based sighting system was replaced by a laser rangefinder-based version sometime during the production run, at an unknown point. New turrets lacking the protrusion for the second optic port for the coincidence rangefinder were devised for these variants.


Object. 176 (T-72A) 1979-1985

First serious modernization of the tank. Almost everything was changed; the tank had a revised hull armour and a new turret with a composite filler was implemented, the D-81TM cannon was installed, the 902V "Tucha" smoke grenade system was added, a new convoy light with a digital numerical display was installed, and more.


Object. 184 (T-72B) 1985

Second serious modernization of the T-72. The new tank featured completely revised hull and turret armour, a new autoloader, a guided missile firing capability, a new cannon, a new engine, and more. Officially adopted in October 27, 1984, but the first order from the Ministry of Defence was issued in January 23, 1985.


Object. 184-1 (T-72B1) 1985

Downgraded T-72B variant without the missile firing capability and with the original Ural autoloader. This aspect of the T-72B1 is examined later on in the article, in the section on the autoloader.



Again, it must be stressed that this is only a very basic list of variants. It is unwise to generalize with regards to the T-72, as the model designation sometimes does not reveal the full story. For example, the T-72 Ural-1 had the T-72A composite armour turret since 1977, but retained its old optical coincidence rangefinder and kept the designation of "Ural-1".


Table of Contents




  1. Commander's Station
  2. TKN-3M
  3. Commander's Fire Controls
  4. Communications

  5. Gunner's Station
  6. Sighting Complexes
  7. TPD-2-49
  8. 1A40
  9. 1A40-1
  10. Auxiliary Sights
  11. TPN-1-49-23
  12. TPN3-49
  13. 1K13-49
  14. 1A40-4 Sosna-U

  15. Stabilizers
  16. 2E28M "Sireneviy"
  17. 2E42-2 "Zhasmin"
  18. 2E42-4 
  19. Meteorological Mast
  20. D-81T Cannon
  21. 2A26M-2
  22. 2A46
  23. 2A46M
  24. 2A46M-5

  25. Ammunition Stowage
  26. Autoloader
  27. Loose Stowage

  28. Ammunition
  29. HE-Frag
  30. HEAT
  31. APFSDS

  32. PKT
  33. Anti-Aircraft Machine Gun



Due to length restrictions, this article has been divided into two parts. Part two is available here.




COMMANDER'S STATION


From Stefan Kotsch's fantastic website

The commander's station is somewhat cramped, which can be exacerbated by bulky winter clothing, but still noticeably less cramped than the gunner's station, which is suitable since his duties involve more movement. If we refer to this diagram from "Human Factors and Scientific Progress in Tank Building" by M.N. Tikhonov and I.D. Kudrin as provided by Peter Samsonov, we can see that the commander of a T-72 has much less space (0.615 cubic meters) compared to a T-55 commander (0.828 cubic meters), but this is obviously not possible. For one, the commander in a T-55 has to wrap his legs around the gunner seated in front of him - because there is simply not enough legroom - and the breech guard squeezes him against the turret wall. It is the exact opposite for the T-72. As the commander's station in the T-72 is completely separated from the gunner's station, there is nothing in front of him below chest level, and as a result, he has all the legroom in the world. According to Sergey Suvorov, the use of an carousel-type autoloader in the T-72 as opposed to a basket-type autoloader as in the T-64 reduced the vertical space in the tank by around 25 cm. For this reason, the crew in the turret must sit with their legs stretched horizontally as if they are sitting on the floor of the tank. Even so, the amount of legroom is more than adequate.

The commander's upper body is less well accommodated, but it is still a huge improvement over the T-54, as much of the equipment attached to the wall of the commander's station (like the bulky radio) has been moved forward so as to free up more space for his shoulders, as you will see in the many photos below. Overall, the T-72 definitely offers more space for the commander than a T-55, though that may not be very high bar to pass.

According to this presentation from the TASS news agency, the turret compartment has a volume of 5.9 cubic meters, presumably total space, while the driver's compartment has a volume of 2.0 cubic meters and the engine compartment has 3.1 cubic meters of volume, for a grand total internal volume of 11.0 cubic meters.


The commander's cupola follows the same pattern set by the cupola of the T-54, but with some significant differences. The T-72 cupola is taller, has more thickly armoured hatch, and the hatch has a clam shell shape rather than a simple half-moon shape. In terms of width, the two cupolas are very similar in diameter. The race ring of the T-72 cupola extends below the turret roof, whereas the one in the T-54 cupola doesn't. This is because the T-72 cupola has an extra toothed ring to engage the counter-rotating motor - we will explore this further later on.



T-72 (left), T-55 (right)


The cupola housing is secured to the cast steel turret roof by a ring of bolts around its circumference, but unlike the T-54 cupola, the bolts are sheltered against gunfire and the weather. The T-72 cupola is also more complex as the race ring it runs on is not directly connected to the fixed base bolted to the fixed cupola housing but to an intermediate metal band, and that connects to the cupola housing via a larger race ring. The intermediate metal band is between the inner cupola (which carries the optics and hatch) and the fixed base, and the anti-aircraft machine gun mount is installed on this band. By releasing a locking mechanism, the intermediate band can be freed from the fixed base, thus allowing it and the machine gun installed on it to be rotated degrees independently of the rest of the cupola, as you can see in the photo below (photo from Russian Ministry of Defence).




The independence of the machine gun mount from the cupola is demonstrated in this video, and in this video. This video from TV Zvezda shows a fully assembled turret with the machine gun cradle on its mount, traversed to a forward position. This aspect of the cupola is further discussed in the section on the anti-aircraft machine gun later on.

I could not find the diameter of the cupola or the dimensions of the hatch, but by scaling the TNPA-65A periscope housing to the rest of the cupola in the diagram, I found the diameter of the hatch to be 665mm, and the maximum width to be 413mm. Those are only the external dimensions, however. The interior dimensions are probably 2 to 3cm smaller.


A snug fit ensures that the commander will not be rocked around too violently while traversing difficult terrain, but it also means more things to knock into, and it can get uncomfortable in hot weather. Like in the gunner's station, the commander is ventilated by a single adjustable DV-3 plastic fan, a simple 5.2W fan running on the tank's 27V electrical system. The DV-3 is shown in the photo below.




The DV-3 is closely related to the DV-302T, which is a very similar plastic fan used in aircraft like the Mi-8 helicopter, Il-76 and many more. In other words, the DV-3 was essentially an off-the-shelf product at the time the T-72 began mass production.

Because the commander has his own hatch, he may opt to simply stick himself out of the hatch and ride on the turret roof. Still, the negatives of the crampedness of the station outweigh the benefits, especially in winter time.

The amount of legroom afforded to the commander is more than adequate. Due to the ammunition carousel of the autoloader, the internal height of the hull is somewhat limited, but the horizontal space is unaffected. The commander can stretch his legs out as far as he desires.


The commander's main means of battlefield surveillance is a forward-facing TKN-3M pseudo-binocular periscope, augmented by two rectangular TNPO-160 periscopes on either side of it and two narrow TNPA-65A viewing prisms aimed to his rear quarters. There is no periscope that allows the commander to see directly behind the turret. For that, he must spin the cupola just a little to one side, and look out of either one of his TNPA-65A viewing prisms. All viewing devices are electrically heated using the RTS system to prevent fogging in cold weather. RTS stands for "Регулятор Tемпературы Стекла" (Regulyator Temperatur' Stekla), which means "Glass Temperature Regulator".




The two photos below show the TKN-3MK, a slightly updated version of the TKN-3M. It is impossible to visually distinguish them from each other - the only way to know is to see what model of T-72 you are looking at.




As for equipment, the commander's station is packed chock full of various knick-knacks essential for commanding the tank. There is also an assortment of accessories that are not directly related to his job, but are placed near him because it was the only available space in the squeezed turret.




In the photo above, we can see the R-123 radio transceiver (BLUE) at the very bottom. The silver-gray box above it is a switch box (RED) for the communications system to switch between radio and intercom communitcation, and the white box beside it is a master control panel (GREEN) for most of the functions in the tank. This control panel (pictured below) gives the commander dominion over things like the lights and the ventilator, and behind the silver and milk-white metal flaps at the corners of the panel are the emergency engine stop button and the emergency fire extinguishing system engagement (activates all the fire extinguishers connected to the automatic firefighting system in the fighting compartment) button, respectively. This control panel also enables the commander to initiate the autoloader.




The commander is responsible for setting the fuse on HE-Frag shells, and this control panel enables him to do so. Pressing one button partially activates the autoloader so that it stops before the ramming cycle commences. The commander will then use his special fuse setting tool to set the fuse to either the High Explosive or Frag mode. Then, another press of a button finishes the loading procedure.


The silver box (YELLOW) to the right of the intercom switch enables the commander to control the autoloader for the purpose of unloading it.




The box flips open to reveal control toggles for operating the individual elements of the autoloader system, like raising and lowering the shell casing catcher, opening and closing the ejection port, activating the rammer, and so on. If the autoloader is only partially malfunctioning, the commander can use this control box to operate some parts of the loading procedure automatically, and operate other parts manually. If the autoloader carousel malfunctions, it is possible to rotate the carousel manually, and crank the autoloader elevator by hand to extract ammunition and use the electric chain rammer to ram the ammunition into the breech.


Above that is a TN-28-10 dome light and the already-mentioned DV-3 plastic fan. The dome light is part of the PMB-71 lighting system.  At the upper left corner is a wooden dowel with a rubber head. This is a ramming stick for the commander to use when manually loading the cannon. Beside the dome light is the gyroscopic tachometer for the stabilizer system.

Besides the dome light in front of the commander, there is another dome light light directly above the gun breech, making it quite easy for him to perform his duties, including loading and unloading the autoloader and loading the co-axial machine gun.


Here is another view of the station, this time from below. Photo from KyivPost.




Toggle switches for turning on the external and internal lights and the periscope heating system are located around the cupola ring. Two such switches are shown below. The switch on the right is to turn on all of the forward facing lights on the tank, and the switch on the left is to turn on all of the rearward facing lights.






TKN-3M, TKN-3MK




The TKN-3M is a combined pseudo-binocular periscope with night vision capability in two modes; passive and active. The periscope itself has a fairly average angular FOV of 10 degrees in the day channel, or 8 degrees in the night channel. The periscope has two eyepieces, but only one aperture, making it a pseudo-binocular periscope. Since it is not a truly binocular periscope, the TKN-3M offers practically no depth perception. This does not make much difference at long distances, but the viewing experience may take some getting used to. The single aperture of the periscope is seen below.




It has a fixed 5x magnification in the day channel and 3x magnification in the night channel. This is quite limited, making long-distance observation problematic, especially if the weather is unfavourable. It can be manipulated to elevate and depress to a reasonable degree, offering some limited aerial view for the commander. Due to the fact that the periscope is unstabilized, identifying another tank at a distance is very difficult while the tank is on the move over very rough terrain. The commander is meant to bear down and brace against the handles of the periscope to control his line of sight, and that is adequate for keeping the target within view for the smoother parts of off-road driving, but the degree of accuracy is not enough for range finding or precise target designation. Overall, it is not a great system, and it was outstripped as early as 1973 by the new TRP 2A sight installed on the Leopard 1A3, and by the highly advanced PERI-R12 panoramic surveillance and sighting system installed in the Leopard 1A4 in 1974. Both of these devices were capable of very high magnification and had powered traverse with stabilization, and the PERI-R12 had the additional function as the sighting complex for the commander when he used the gunnery override mode. Having this ability in an independent surveillance device was a breakthrough for the early 70's, and many tanks would not have a similar feature until the late 80's or 90's.

In the passive mode of operation, the TKN-3M employs a 1st Generation light intensifier tube, which is usable in lighting conditions as dark as a typical moonless, starlit night (0.005 lux). As the amount of light increases, the effective viewing distance increases. An enemy tank can be identified at up to 400 meters at 0.005 lux ambient light, but identifying the same tank is entirely possible at slightly further distances in moonlit nights, but excess brightness cannot be tolerated as the image intensifier tube may be damaged from the power surge. The two most significant advantages of the passive imaging system is that no infrared light is emitted, unlike an active infrared imaging system, and the image intensifier system enables the commander to detect the minute amounts of visible light emitted from enemy IR spotlights and headlights from long distances.

To switch between the day and night channels, the user simply rotates a dial on the right side of the periscope housing by 90 degrees. This flips an internal mirror by 90 degrees, thus changing the optical path between the night vision unit and the regular daytime optic. The diagram below shows the two choices. Diagram (a) on the left shows the path of the light from the aperture through the night vision system and into the eyepiece, while diagram (b) on the right shows the mirror flipped 90 degrees and the light from the aperture passing through the normal optical channel for daytime use.




The TKN-3MK is a slightly updated variant with a 2nd Generation image intensifier system, producing a brighter and clearer image, but the viewing distance is hamstrung by the low 3x magnification factor.  nominal tank identification range of 500 meters under the same lighting conditions stated before (moonless, starlit nights with ambient light levels of 0.005 lux). 2nd generation image intensifiers differ from their 1st generation counterparts by the implementation of an MCP, a so-called "electron multiplier". The addition of an MCP substantially increases the amplification factor of the device compared to a 1st generation image intensifier, but the price of a 2nd generation image intensifier is also much higher. All T-72B tanks are equipped with the TKN-3MK. Sadly, even the latest modifications of the T-72B3 is also equipped with the TKN-3MK, which is entirely inappropriate for its time.

Besides passive image intensification, the TKN-3M/K features an active infrared imaging system using an electron-optical converter that allows the device to pick up infrared light, convert it into visible light, and amplify it to a sufficient brightness. The active mode requires the use of the OU-3GK IR spotlight which is mounted on the rotating cupola. Inside the spotlight is a rather low-powered tungsten filament lamp designed to run on 110W when connected to the tank's electrical system.




The distance at which a tank-sized target can be identified in the active mode is apparently around 400 meters, although the spotlight illuminate objects much further away than that. The main issue is the low resolution of the image and the low magnification factor.

Overall, the TKN-3M offers very poor night viewing capabilities compared to modern thermal imaging sights, but it was at least equally advanced as other image intensifier optic built in the 60's (the TKN-3 first appeared in 1964 on the T-62), and the use of image intensification technology was a completely novel feature, up until the 70's. From the 70's onwards, the TKN-3 was outstripped by more advanced Western passive image intensifying optics.


The periscope aperture has a small wiper, as you can see in the photo below.




Rotation of the cupola can be done by either using the handgrips on the TKN-3 to slide the cupola around the race ring, or by using the cupola-mounted anti-aircraft machine gun cradle's handles, if the commander is outside the hatch. By rotating the cupola, the commander can attain a full 360 degrees of vision.

At the end of the left hand grip of the TKN-3M is a button to designate a target for the gunner, in the same way as the hunter-killer T-54B system with the TPK-1. Unlike the T-54, though, the T-72 features an additional electric motor that automatically counter-rotates his cupola so that his original orientation is preserved while the turret is spinning. The photo below shows the direction sensor, painted red, in contact with the three metal bands on the cupola ring above the golden toothed band. These metal bands interface with a roller inside the direction sensor, and the sensor detects which direction the cupola is facing relative to the turret by detecting the direction in which the roller is deflected. The counter-rotating motor is the silver box, underneath the red direction sensor, as seen in the photo below. The counter-rotating motor spins the cupola through a drive gear in contact with the toothed band around the circumference of the cupola ring.




Once the turret is slewed towards the target, the gunner will see the target, lay the gun more precisely, and then engage. The commander has duplicated controls for ammunition selection, so can select the most appropriate shell type for the type of target upon spotting it, allowing the gunner to open fire as soon as he has laid the sights on target. This sort of cooperation between the gunner and commander helps the T-72 to attain a higher rate of fire.

It is worth noting that while the target designation system is activated with a single click of the left hand grip button on the TKN-3M periscope, the button can be held down to slave the turret to the commander. Wherever he aims the reticle, the turret will follow. Turret rotation is always done at maximum speed, so small corrections in turret orientation may be a little jerky.


The TKN-3M sight has a stadia reticle intended for approximate manual range estimation of tank-sized targets 2.7m tall from a distance of 800m to 3 to 3.2km, although this might be slightly optimistic for most situations. However, it is entirely possible for the crew to see and engage targets at such distances if weather conditions and the geography of the battlefield allows for it. Example of such geography should include plenty of high ground. Stadiametric ranging is not an accurate way to determine target distance. At long distances, the errors in estimation may amount to hundreds of meters.








A horizontal stadia rangefinder is objectively superior to a "choke" type stadia rangefinder, like the type found on M551 Sheridan light tanks. Whereas a "choke" rangefinder indicates target distance based on width, a horizontal rangefinder depends on height instead. A "choke" rangefinder would not be able to accurately determine distance if the target tank was not oriented directly towards the observer, which meant that against both stationary and mobile targets, and especially targets moving side-to-side, it would be mostly useless for actually finding range. Keep in mind that depending on the direction which a tank could be travelling, the observer could be seeing the tank lengthwise and not its actual design width. It would also be impossible to accurately guess a target's real width given a silhouette of an unknown size. A horizontal-type rangefinder, on the other hand, can measure distance no matter which direction the target is travelling in, and if a tank was in a hull-down position, the height of a tank would generally be halved, given that only the turret is exposed, giving the observer a fighting chance to approximate target distance.


As mentioned before, the TKN-3M sight depends on an OU-3GA xenon arc IR spotlight for illumination when operating in the 'active' mode. An inherent shortcoming to the usage of IR spotlights is that enemy tanks using a sight operating on the same type of system can see the light as well, along with its source. The SVD sniper rifle, for example, was fitted with the PSO-1 scope with an IR filter that let the sniper exploit this trait and allowed him to see enemy tanks at night. This makes it easy for the T-72 to be caught in an ambush at night by other tanks of the era like M48s, M60s, Leopard 1s, Chieftains, etc, although it must be said that the inverse also applies. The T-72 can easily see and engage enemy tanks maneuvering in the dark without switching on its own spotlight. Like turning on a flashlight in the dark,you may not be able to see very far, but anyone can spot your torch from miles away. 




COMMANDER'S FIRE CONTROLS



None of the Soviet era T-72 models featured a set of firing controls for the commander. This feature only came on the recent T-72B3 modernization. Before, the commander only had access to the autoloader controls, but in the T-72B3, the commander is now equipped to override the gunner entirely. He has a flatscreen display linked to the Sosna-U sight, and the necessary controls for firing the main gun and the co-axial machine gun at his disposal in the form of a set of handgrips similar to the gunner's. This arrangement is no different from what most Western tanks already had for decades.




The control unit is almost exactly the same as the type installed in the T-80 tank as part of the PNK-4 fire control system. Control of turret traverse and gun elevation is accomplished using the thumbstick. The decision to use a thumbstick was because a full joystick could not be easily manipulated with precision if the operator's body and arm was rocking around if the tank were going over rough terrain. However, the thumb would be completely stationary if the hand was securely gripping a handle. The index finger rests on the trigger.






COMMUNICATION






The T-72 was originally supplied with an R-123 radio. The R-123 radio had a frequency range of between 20 MHZ to 51.5 MHZ. It could be tuned to any frequency within those limits via a knob, or the commander could instantly switch between four preset frequencies for communications within a platoon. It had a range of between 16km to 50km. The R-123 had a novel glass prism window at the top of the apparatus that displayed the operating frequency. An internal bulb illuminated a dial, imposing it onto the prism where it is displayed. The R-123 had an advanced modular design that enabled it to be repaired quickly by simply swapping out individual modules.

Beginning in 1984, the R-123 was replaced by the R-173 radio in the new T-72B. The R-173 had a frequency range of between 30 MHZ to 75.999MHZ and 10 preset frequencies. It had an electronic keypad for entering the desired frequency, and a digital display. Both the radio and intercom system are directly routed to the throat mike and headset, which are integral parts of the iconic Russian tanker's helmet.



The throat mike facilitates good voice clarity as it doesn't pick up any ambient noise, making a throat mike system inherently superior to open mikes. However, this is counteracted by the very poor sound quality from the headphones installed in the helmet. It is more pleasant for the commander to shout commands to the other crew members rather than use the intercom.


Communications through the R-173 are rather easy to intercept and jam or listen in to. For instance, Chechen fighters during the Chechnya campaign were able to listen in to radio chatter and even interject bogus commands over Russian airwaves. For this very reason, the new, frequency-hopping R-168-25UE-2 was rapidly launched into service in the 2000's to replace it.

R-173

The R-168-25UE-2 frequency-hopping encrypted radio set is used for communications on all levels. It replaced both the R-173M and R-123 radio stations in the T-72B3 modernization.

R168-25UE-2

The R-168 family of radios is now the standard throughout the Russian ground forces, from infantry platoons to tank companies. It can produce frequency hops 100 times a second, and the data is encrypted as well.

Command variants of the T-72 were equipped with an additional R-123 radio. As of today, the R-123 radio is completely antiquated. It is an analogue design first used in the T-62 back in the early 60's to replace the R-113. Command variants were identifiable via their distinctively elongated second antenna.

The modern day Russian army no longer fields command variants of the T-72 due to a drastic shift in combat doctrine. Instead, all modern T-72B3 tanks have only a single R-168-25UE-2 radio. Command variants of Soviet era T-72s have been reverted to their base variants.

Besides the updated communications hardware, the tank's intercom and radio control panel was also replaced with an all-new digital one shown below:




Unlike some NATO tanks like the M60A1, the commander's means of surveying the battlefield is conducted with periscopes and not with vision blocks. The commander's head is located below the cupola ring as well. The implications of this design decision is that the commander has rather unremarkable all-round visibility compared to an American tank with their large cupolas and large vision blocks, but like all design decisions, this one has a few advantages of its own. The commander is completely withdrawn from large-caliber sniper fire (12.7mm-type) and concentrated machine gun fire directed at the cupola. There is absolutely zero chance that his eyes may be injured by broken glass due to the nature of the periscope and because the periscope eyepiece is protected by ballistic glass, as shown in the photo below, to the left.




For forward observation, two TNPO-160 periscopes are provided. They have a total horizontal range of vision of 78 degrees, and a vertical field of view of 28 degrees; 12 degrees above the horizontal axis and 16 degrees below.

Two TNPA-65A periscopes bring up the 4 o'clock and 8 o'clock positions. They are mounted directly in the hatch, and give the commander a view of the rear two quadrants of the turret. Unfortunately, there is a blind spot directly behind the cupola, since this is where the hatch's locking latch handle is located.



TNPA-65A provides only 14 degrees of binocular vision horizontally and 6 degrees of vertical vision, meaning that its width is within the normal and acceptable range, but it is very narrow.

The TNPO-160 periscopes with the TKN-3 binocular periscope comprise the forward vision assembly of the commander. Despite the limited all-round visibility (compared to NATO tanks) offered by the commander's five periscopes, he can still compensate by simply rotating his cupola. This essentially negates the smaller number of observation devices, but it does not compensate for the periscopes being more constricted than the type found in typical NATO tanks. Nevertheless, while the commander may not have perfect immediate all-round awareness, he has a very reasonable degree of coverage, definitely enough to fight with.




The commander's hatch is of a forward-opening half-moon type, mounted on the rotating cupola. The hatch is quite small, and exiting through it in a hurry may be problematic if the commander is wearing winter clothing.

It is spring-loaded to assist the commander in opening the heavy hatch. A simple rotating handle locks the hatch when closed, preventing it from bouncing up and down when the tank is in motion, and a smaller handle at the bottom of the hatch serves to lock the hatch in place when it is opened, which is useful when the commander wishes to view the battlefield from outside the hatch, or when he needs to use the complementary cupola-mounted machine gun..



Because it opens forward, the thick hatch gives the commander full-body protection from machine gun fire whenever he wants to pop out for a tactical assessment with binoculars. To look over the hatch, all he needs to do is to stand on his seat.

The commander is shielded from machine gun and sniper fire by his hatch

In some modifications beginning in the mid-70's, the commander's cupola may also have peculiar shield installed forward of the hatch. All T-72s operated by the Russian ground forces today feature this shield.




The lower part is a simple hanging canvas sheet, which isn't intended to be part of the protection scheme. The upper part is just a face shield for the commander for if he were to sit outside on the turret while on road marches, probably to protect his face from bugs.




The shield made of very thin sheet steel with an equally thin polycarbonate or perspex window and is thus not bulletproof, splinter-proof or fragmentation-proof (though the commander's hatch is). Therefore, the protection afforded to the commander does not change. The only ballistic protection the commander gets still comes from his hatch, only now he has dust and bug protection. See the photos above and below.






GUNNER'S STATION






The gunner's station is dominated by the massive GPS (Gunner's Primary Sight), which tips the scales at 80kg. He is responsible for all of the weapons-related equipment, including the autoloader, stabilizer, cannon, co-axial machine gun, the sighting devices and their associated instruments.

The gunner's station is the most cramped position in the T-72, and even more so if he is wearing winter clothing. However, it would be a mistake to consider the cramped nature of the gunner's station as a unique and defining feature of the T-72. As a whole, the T-72's turret does indeed have a much smaller volume than most tanks, but the space delegated to the gunner is very much on par with its contemporaries.

Looking again at this diagram from "Human Factors and Scientific Progress in Tank Building" by M.N. Tikhonov and I.D. Kudrin as provided by Peter Samsonov, we can see that the space afforded to the gunner is seriously tight, only 0.495 cubic meters. However, this is a big improvement over the T-55, which gave its gunner only 0.395 cubic meters of space.

In any case, internal space in this tank seems to be more psychological than physical. Volume and comfort-wise, the gunner's station in a T-72 is quite adequate for a legacy tank, though still undoubtedly cramped. However, that is not to say that crampedness of the gunner's station is entirely negative. A snug fit ensures that the gunner will not be knocked around too much while the tank is in motion, which is undoubtedly a small benefit to targeting precision while driving on uneven ground. It isn't so much an issue while on long marches, because both turret occupants may simply sit on the turret roof instead. In this respect, the T-72 has a slight ergonomic advantage over many tanks in that the gunner has his own hatch and he can exit whenever he likes to sit on the roof, or to stand upright. In the event of an internal fire,the entire crew can bail out with no fuss. This is quite unlike tanks like the T-55, Leopard 1, Abrams, or indeed, any other manually-loaded tank except for a few oddball designs like the M60A2. Usually, the gunner is not provided with his own hatch. On long marches, he might be forced to stay put in his decidedly cramped station for hours at a time.


Case in point: in Part 2 of his "Inside The Chieftain's Hatch" video review of the Centurion tank, Mr. Nicholas Moran from Wargaming noted that after just 20 minutes, it was beginning to get uncomfortable in the gunner's seat. If it began to get uncomfortable in his seat, the gunner of a T-72 can open his hatch and sit on the roof, or just stand on his seat and stretch. Additionally, in a typical manually loaded tank, if the commander were incapacitated or killed, the gunner would have to squeeze through the commander's body or shift it aside in order to bail out. This is not a problem for the T-72.




Mr. Moran also noted that the gunner's station in the T-55 was very well laid out, but mentioned that legroom was somewhat limited unless the turret was pointing straight forward, in which case he could stretch his legs all the way into the driver's station. The T-72 fully preserves the reportedly excellent layout of the T-55, but is more spacious by 0.1 cubic meters and offers the same great legroom no matter where the turret is pointed. This is not due to the lack of a turret basket, but to the large turret ring diameter and separated seating of the commander and gunner.


Ventilation is provided by a DV-3 plastic fan, like in the commander's station. It is more than enough in European climates where temperatures are usually around 20° C (68° F) or less, as it is a relatively powerful 5.2W fan, but in hot, desert regions averaging 30° C to 40° C is only useful for increasing air circulation to stave off stuffiness, and little else. Still, it's better than some tanks that do not provide any personal ventilation at all.


For general visibility, the gunner is provided with a single forward-facing TNPO-165 periscope and another TNPA-65A periscope on his hatch, pointing to the left. The TNPO-165 periscope has a large field of view. It is placed there for the gunner to check the orientation of the gun barrel, and to make sure that if the tank is entering a ditch or a trench, the gun barrel is elevated safely. In daytime, the periscopes are also sources of light.


1A40-1 sighting complex and 1K13-49 night vision/auxiliary sight

As you can see in the photo above, the gunner is supplied with a duplicate of the commander's master control panel. Besides being able to initiate the fire control system, control the ventilation, turn on the lighting system, and much more, having the master control panel gives the gunner complete control over most of the electrical equipment in the tank, and also enables the gunner to set the fuse on a HE-Frag shell in lieu of the commander if necessary. This means that technically, the T-72 can fully operate on a 2-man crew with a minimal loss in combat capability. This may be useful when a tank company or battalion is understaffed and there are no sufficiently qualified substitutes for the tank commander's position.


The circular box between the TPD-K1 eyepiece and the handgrips is the AZ-172 autoloader control box. The autoloader is turned on from this box, and the ammunition type can be selected by the gunner.




The T-72B uses a different autoloader, sometimes referred to as the AZ-184, and the control box is also different as a result. With the introduction of a new ammunition type, the new control box has an additional option on the ammunition selector dial: missiles. The T-72B3 features a modification of the AZ-184 autoloader, and it can be seen in the updated control box. The new control box retains the same layout as the old one, but is digitized.




In a high tension tank duel, a good gunner will have his right hand on the handgrips to pull the trigger, and his left hand on the loading switch, so that at the moment immediately after firing, the autoloader will kick into action. The autoloader control box can be used to set the autoloader to automatic operation or manual operation. Setting it to manual operation mode enables the crew to manually load the gun with partial assistance from individual components of the autoloader, such as the chain rammer, or to manually load the gun entirely by hand. If the crew intends to load the cannon manually, setting the autoloader to the manual mode is mandatory because it locks the stabilizer to fix the gun at a certain angle for easier loading and to prevent any accidents from occurring. It also lets the sighting complex recognize the readiness of the cannon once a shell is loaded.

The gunner is also provided with an autoloader ammunition indicator. The indicator is rather crude, even for its time, as the indicator display is based on simple milliammeter technology. Due to the small size of the indicator pin, it may be difficult to easily see the indicated number in a high intensity situation.




The indicator does not have any selectors or dials on its own housing. Rather, it works in conjunction with the autoloader control box. When the gunner selects an ammunition type on the dial on the autoloader control box, the ammunition indicator automatically displays the ammunition reserve for that ammunition type currently stowed in the autoloader carousel. The number of empty slots in the autoloader carousel is determined by setting the ammunition selector dial to the "Load" position. The ammunition indicator only goes up to eleven, so if the number of rounds for any ammunition type exceeds eleven, the exact number of rounds can only be determined by finding out the number of rounds of the other ammunition types and the number of empty slots in the carousel. Needless to say, it was not a very good system.


Besides the autoloader controls, there is also a turret azimuth indicator, installed just next to the manual turret traverse flywheel.




The indicator is akin to a clock, with an hour hand and a minute hand. The hour hand is mainly a tool of convenience as it shows the direction the turret is pointing to, but it is also an important tool for laying the gun for indirect fire. The minute hand is read with the hour hand to obtain a precise reading of the orientation of the turret for indirect fire purposes.


The gunner is provided with a single half-moon hatch. Its most distinctive feature is the smaller circular port hole at its center, intended for snorkel installation.




The hatch is spring loaded to hold it in place when open, and to give a little leeway for the gunner when opening it. It is locked with a simple rotating latch. There is a single TNPA-65 periscope embedded in it, pointing to the left (mentioned above). It is rather small and slit-like, but it provides the gunner with some precious limited sideways visibility. It provides only 14 degrees of binocular vision horizontally and 6 degrees of vertical vision.



In the gunner's case, periscopes are not very useful on a day-to-day basis. For one, the gunner must concentrate on his job of gunning the gun, and he will not be able to see much from out of the few vision devices that he has. Still, the periscopes are useful for letting outside light in, and they give him a decent sense of his surroundings, all the better for the gunner when buttoned up.




SIGHTING COMPLEXES



Because of the T-72's status as a "mobilization model", the more expensive parts were usually kept as affordable as possible. It was to be manned by conscripts with minimal training (though I emphasize that it was still much better and more thorough training than what many 3rd world country tank crews received), and T-72 crews received fewer opportunities to conduct firing exercises during peacetime than T-64 and T-80 crews. The sighting systems suffered the most from this practice. The T-72 never had a true ballistic computer and the fire control system required far more manual input than the best analogues of the time. Furthermore, T-72 units usually received new ammunition later than units equipped with the T-64 or T-80. This fact exacerbated the lack of sophisticated sighting devices, and this shortage of technology in an increasingly technological stage of the Cold War was not comforting.




T-72 Ural


TPD-2-49


The T-72 first entered service in 1973 sporting the TPD-2-49 sighting complex with an integral optical coincidence rangefinder. The sight is independently stabilized in the vertical plane. The internal gyroscope installed at the far end of the sight housing, in a protruding block underneath the sight aperture. The vertical stabilizer of the cannon is slaved to the sight. This improves the accuracy of the cannon in the vertical plane.


The viewfinder is split into two halves, top and bottom. The two measuring optics see the same target, but half of it is blocked out, and the gunner must use the adjustment dial near his hand grips to line up both halves and obtain a seamless picture. This process was cumbersome and somewhat inaccurate - the error margin was 3% to 5%, which meant that the range could be off by up to ±200m at 4000m, or a much less serious ±30m at 1000m range. However, it's worth considering that the average tank engagement distance expected in Europe was estimated to be 1500 m, not to mention that the use of hypersonic APFSDS ammunition meant that the error margin could usually at closer ranges be ignored since the ballistic trajectory was so flat that amount of drop was completely negligible at out to 1500 m or more. The problem was much more pronounced with HEAT and HE-Frag ammunition, which were heavier, had more drag and came out of the barrel at much lower velocities. With the advent of long range ATGM systems mounted on jeeps, scout cars, IFVs and even light tanks, accurate long-distance fire with HEAT and HE-Frag shells was imperative.

The sight has a fixed 8x magnification with a field of view of 9 degrees. The second measuring optic also has a fixed 8x magnification, but has a much smaller field of view of only 2 degrees.


Because TPD-2-49 is independently stabilized in the vertical plane, it is possible to conduct rangefinding while the tank is in motion. There are two eyepieces for this system. The left eyepiece shows the view from the aperture of the sight itself, while the right eyepiece is from the second optic; the second eye of the binocular pair.




The gunner turns a range adjustment wheel located just above his hand grips to line up the two halves, as shown in the GIF below and in this short video (link).




The gunner keeps both eyes open, but make no mistake, the rangefinder is not stereoscopic. The gunner sees one half of the target from each of the eyepieces, but since the field of view from the second measuring optic is very narrow (2 degrees) compared to the view from the main sight (9 degrees), the gunner must find the target using his main sight and then place target near or at the center of the viewfinder of the main sight, or the target will not be in view of the second measuring optic. See the diagram below.




In case of low visibility from poor weather conditions or from enemy countermeasures, the rangefinder can be set to a secondary mode, where instead of splitting the target into two halves, two full images of the target are displayed on top of one another. There is a fixed vertical line at the left side of the viewfinder, and the gunner must lay the line on the edge of the target tank in the bottom image by using his handgrips, then turn the range adjustment wheel until the same edge of the target tank in the top image touches the line. In other words, if the same part of the tanks in both images touch the vertical line, then the two images are aligned. Refer to the diagram below.



This method is less precise, but may be easier to use if the outline of the tank is not clear or if the target is not a tank but something with an irregular shape.


A major flaw with optical coincidence rangefinders in general is that they don't work very well on camouflaged targets, especially without a high magnification sight. Even tanks simply painted the same shade as the environment can be difficult to accurately range because the outlines of the tank may not be very clear to the gunner. As mentioned before, ranging errors were more or less irrelevant to the T-72 because it fired very-high-velocity APFSDS ammunition, but firing HEAT on targets would be very difficult at longer ranges, not to mention moving ones.

While the TPD-2-49 would have qualified as among the world's best sighting systems when it was introduced with the T-64A in 1967, it was not quite as fresh by the time the T-72 Ural came onto the scene in 1974. As time went on, it became increasingly clear that optical rangefinders were no longer satisfactory, largely because it took a great deal of concentration from the gunner to operate, and in the case of the TPD-2-49, it was very expensive to manufacture an advanced independently stabilized sight with an integrated optical rangefinder. They were also fragile, despite extensive shockproofing and anti-vibration bushings. Any misalignment as a result of shocks from tank shell impacts could cause some lens to be misaligned even slightly and that would be enough to put it out of commission, and this was a big problem with the T-72 (and indeed, every other tank with such a rangefinder) because an optical tube connecting the first aperture to the main sighting unit ran across the turret ceiling above the cannon breech block. A shell impacting the turret roof might bounce off and not penetrate the steeply sloped armour, but the impact and the shifting of the relatively soft and relatively thin cast steel roof could cause enough damage to the optical tube that it might not be usable. The optical tube connecting the two apertures can be seen in the photos below (credit to t-72.de)




This, in addition to the issues mentioned above, meant that production of TPD-2-49 sighting complexes was summarily discontinued just two years later in 1975 and the Ural-1 modernization programme to refit T-72 Urals with TPD-K1 laser rangefinding sights began in that same year. The Ural-1 modernization retained the turret of the Ural, but only swapped out the sight. Since it was of no use anymore, the second optic port for the rangefinder aperture was blocked off and permanently welded shut.


TPD-2-49 placed the T-72 Ural on at least equal footing with the best NATO tanks at the time, including the Leopard 1. As the optical coincidence rangefinder was integrated into the sight and the whole package was independently stabilized (which no other system could boast of), the TPD-2-49 could be considered a rather advanced sighting complex of the time, on par with the fire control system of the Leopard 1 and superior to the setup on the M60A1, which had a separate primary sight and M17 rangefinder unit. While the gunner of an M60A1 would have to conduct ranging and then switch over to the primary sight to engage the target, the TPD-2-49 sight was adjusted concurrently with the rangefinder, and target acquisition time was slashed accordingly. The only flaw is that the commander of the T-72 is not able to take over the rangefinding procedure via a sight extension, like on the aforementioned Western tanks.



T-72 Ural-1, T-72A


1A40 Sighting Complex, TPD-K1




The TPD-K1 is part of the 1A40 sighting complex, which included the TPD-K1 itself, plus the internal ballistic calculator and the sight-stabilizer interface. It was first installed on the T-72 Ural-1 modernization, later carrying over to the T-72A in 1979 and to the T-72B in 1985. However, the number of Ural-1 tanks that received this sight is probably quite small, and were probably produced at the tail end of 1978, as it is known that the Ural-1 was still using the TPD-2-49 as late as 1977.

The TPD-K1 sight is very closely related to the TPD-2-49. It has a fixed 8x magnification and a 9° field of view. TPD-K1 gave the T-72 a 3-year head start over its Western nemesis the M60, which received its own AN/VVG-2 laser rangefinder unit in 1978 as part of the M60A3 upgrade. German Leopard 1s did not receive their own laser rangefinders until the 80's rolled around, and British Chieftains had to wait until 1988 to get theirs. 

The TPD-K1 is independently stabilized in the vertical plane, and it has an internal gyroscope installed in the same location as the one in the TPD-2-49. However, the sight is not stabilized in the horizontal plane. This has implications that we will explore later. The stabilizer system for the sight is connected to the cannon for referencing purposes. The mechanical rods that connect the sight (left side) to the cannon (right side) can be seen below. It is a parallelogram-type system.




The cannon is slaved to the sight, meaning that the stabilizer for the cannon is an independent system but its movement is dictated by the stabilizer for the sights. This yields better accuracy.

The sight aperture housing on the turret roof is armoured to withstand small arms fire, and a thin steel shroud extension shelters the aperture from thrown mud, rain, sand and snow. The extended side walls are of a much thicker steel meant to protect from bullets and fragmentation. The aperture itself has a layer of bolt-on SET-5L ballistic glass (19mm thick) to protect it from bullets and shell splinters. The ballistic glass panel comes with an integral heating system to prevent fogging, and it is provided with a small external wiper to remove any debris or mud that might obstruct the gunner's vision.




Tank crews carry an extra sight aperture in internal stowage for quick field replacement.


  


The TPD-K1 comes with a removable solid-state infrared laser rangefinder, but the sight is unusual in that the laser rangefinder is installed inside the sight itself on the right hand side of the housing, but the rangefinder computer is installed outside the sight.

The two photos below show the detached rangefinder processing and readout unit.




The photo below show the rangefinder computer attached to the right side of the TPD-K1 sight module. There is a toggle switch on the computer that prevents the system from accepting ranges of less than 1200 meters or 1800 meters, and placing the toggle switch in the central position lets the system run normally.




According to the Indian Ordnance Factories website, the laser rangefinder uses an IR laser in the 1060 nm wavelength. The rangefinder has an automatic range compensation mechanism for firing on the move, whereby the rangefinder computer will automatically subtract the distance covered by the tank from the final figure. The laser rangefinder has a maximum error of 10 m at distances of 500 m to 3000 m. From 3000 m to 4000 m, the maximum error threshold increases to 15 m. The rangefinder may become unresponsive and highly inaccurate past 3000 meters, so it could be necessary for the gunner to manually dial in the range to the target by other methods. This limitation makes it infeasible to engage targets at distances beyond 3000 m.

The photo below shows a partially opened TPD-K1, exposing the internal PCBs in the laser rangefinder computer.




The rangefinder computer has a digital display to show the measured distance, but range information is ported through to the range indicator dial on the top of the gunner's viewfinder, which the gunner can read. However, reading the range is generally not necessary since the fire control system will automatically calculate a ballistic solution. Knowing the range to the target is only necessary when using the co-axial machine gun, as the sighting complex does not automatically calculate a ballistic solution for it. To lase a target, the gunner must place the illuminated red circle over it and fire off the laser for 1 to 3 seconds. If the target is mobile, it must be tracked within the boundaries of the red circle until the range is obtained. The rangefinder unit must take 6 seconds to cool down between uses.

BVD-2 Range input unit

Range information is automatically routed to the sighting unit, and the sight makes the necessary corrections and adjusts the reticle accordingly. The illustrations below shows what happens during the ranging process.




Firstly, notice the circle at or near the center of the viewfinder. That is where the target must go in order to initiate the rangefinding process. Once that is done, the reticle instantly lowers to account for ballistic drop, and the range indicator dial at the top spins to give a visual reference for the distance (with an accuracy of within 10 m). The lasing circle remains static for lasing the next victim.

This procedure is completely normal in the realm of tank fire control systems, but one oversight is that the path for the laser beam is not merged into the same lenses for the main optic. Rather, the laser rangefinder has its own optical path parallel to the lens tube which the gunner uses. This is evident when you closely inspect the sight aperture:




As you can see, the mirror is divided into two halves by an opaque block in the middle. Underneath the mirror, you can see two apertures. One for the laser rangefinder, and one which the gunner sees out of. This means that the rangefinder circle is never directly on top of the reticle. The gunner must lay the rangefinder circle over the target, lase it, and then finish by laying the reticle on the target. There are a multitude of disadvantages to this. Instead of laying a reticle on the target once and letting the fire control system handle it, the gunner must conduct the laying process twice. This creates room for operator error and consumes precious time.

Without an optical coincidence rangefinder system installed, the optical tube that ran across the ceiling over the cannon breech block in the T-72 Ural is no longer present.




The TPD-K1 has a stadia-reticle rangefinder with markings for distances of 500 m to 4000 m that can be used to gauge target distance if the laser rangefinder is malfunctioning. This and the manual gun laying drives allow the gunner to continue engaging targets even if all aiming systems have completely lost power. The sight will raise and depress along with the cannon when the stabilizer is off because the sight is linked to the vertical manual drive for cannon elevation via mechanical linkages.





All reticle lines can be illuminated (red colour) by an internal light bulb for better discernability in cloudy weather or at night.

The viewfinder of the sight includes graduations for firing the PKT machine gun to a maximum range of 1800 m, for firing HE-Frag shells to a maximum range of 5000 m, for manually applying lead on moving targets, and an auxiliary stadia rangefinder for manually determining the distance to a tank-type target or a bunker 2.7 m in height at distances from a minimum of 500 m up to 4000 m (there is no need for a ballistic solution for targets closer than 500 m). The stadia rangefinder is for emergency use only. On the top of the sight picture is the range indicator dial for the laser range finder, which is also capped at 4000 m. Once the gunner has lased the target, the range will be displayed here for reference is necessary. The range data is automatically inputted into the ballistic calculator.





The ammunition type is automatically inputted into sighting system via the autoloader ammunition selection dial. The silver coloured dial can be seen in the photo above, to the bottom left of the eyepiece of the TPD-K1. When the ammunition type is set, the autoloader begins loading the desired type and the gunner can proceed to lase the target during the loading cycle. Once the gunner has lased the target, the sight automatically adjusts to the appropriate superelevation and commands the weapons stabilizer to do the same. All the gunner must do now is to place the center chevron onto the target and fire. Subsequent shots do not require the process to be repeated, even if the gunner changes shell types or uses the co-axial machine gun. All he must do is select a new ammunition type, and the sight will automatically adjust to the proper superelevation using the range information from the previous lasing.
amm
The inputted ammunition type is indicated by one of three coloured signal lamps at the top left corner of the sight. If the fire control system is being operated manually or in a degraded mode, the sight can be set to the desired ammunition type by turning the dial next to the signal lamps. Otherwise, the ammunition type is automatically inputted.


1A40-1 Sighting Complex, TPD-K1M





According to Mikhail Baryatinsky, newly produced T-72A models from 1982 and onward received the 1A40-1 sighting unit, and the 1A40-1 came standard on the T-72B since its formal introduction in 1985. The 1A40-1 sighting unit features a slightly improved TPD-K1M primary sight and is distinguished from the 1A40 system by the increased number of ballistic variables that may be inputted into the system. The gunner can input ambient temperature, cannon chamber temperature, and atmospheric pressure, in addition to the few original permissible variables from the 1A40 system. The catch was that all of these variables had to be entered manually by the gunner. There were no additional external sensors installed on either the T-72A or the T-72B to automatically record environmental conditions. Variables do not change significantly during the course of battle - like atmospheric pressure - can be entered before or in between engagements, but entering the variables that change dynamically like ambient temperature and cannon chamber temperature is obviously impossible in the middle of a fight.




The sight also includes an additional eyepiece for the gunner's left eye, which is a part of the UVBU lead calculation system. The new UVBU unit calculates the necessary amount of lead for a moving target and displays it in figures which can be manually applied by the gunner on the lateral scale in the TPD-K1M. It works by determining the rate of rotation of the turret as the gunner is lasing the target and then translating that information into mils, which is displayed in the eyepiece for the gunner to read. The gunner will then know which secondary chevron on the lateral mil scale on the reticle he should adopt as the new aiming point. The use of an eyepiece rather than a separate digital display is so that the gunner does not need to break visual contact with the target. As the UVBU eyepiece displays a virtual number on a black background, the gunner can keep both eyes open (and see the number floating in his vision), see the mil figure, and then apply it, all done without tearing his eyes away from the TPD-K1M eyepiece.




The precision of the UVBU unit is not high compared to the systems employed in more advanced fire control systems, as it can only calculate a difference in the angular velocity of the target compared to the tank down to ± 0.5 mils. This is more than enough even for medium range shooting, as a target tank travelling laterally across the sight would be presenting its side profile, but the system is insufficient for long range shooting, but other than that, its most serious drawback is the lack of automation. In the fire control system for, say, an M60A3, lead for the target is calculated and automatically applied to the reticle by the ballistic computer after the target is lased, meaning that the sight automatically adjusts horizontally (via independent horizontal stabilization) so that the reticle has already compensated for lead. This allows the gunner of an M60A3 to press the trigger immediately after lasing - no need to use secondary markings to engage. This is much faster than the system employed on the 1A40-1. This is an inherent flaw in the 1A40-1 sighting complex as it cannot automatically adjust the reticle for lead, since it lacks independent horizontal stabilization. Overall, the system is somewhat crude, and could be considered technologically obsolete the moment it was introduced. By the time the T-72B entered mass production in 1985, the entire 1A40-1 sighting complex could be considered outdated, especially considering the fact that the T-72B did not have a ballistic computer like the T-64B with its 1A33 fire control system.


The TPD-K1M sight itself differs from the TPD-K1 by the presence of mil values printed on the secondary chevrons for the UVBU leading system. Otherwise, the viewfinder is identical.




The photo below (credit to: ru-armor.livejournal) shows the markings more closely.




It is possible to use different shell models by simply twisting a dial on the UVP control unit, pictured below.


Notice the blank spaces on the indicator card; these are left in anticipation of new ammunition. The introduction and use of 3BK-29, for example, would necessitate reprogramming the UVP unit at a depot. The card would then be filled in. Each ammunition type (APFSDS, HEAT, HE-Frag) has 4 slots for different ammunition.

The UVP unit allows the gunner to instantly reset the sights for different types of each category of ammunition. It is also possible for the T-72 to use "exotic" ammunition this way. For example, one of the blank spaces on the indicator card for HE-Frag (labelled OF in the photo above) can be filled for flechette rounds. The gunner can then toggle the sight for the HE-Frag ammunition type, and then cycle the HE-Frag dial on the UVP panel to the flechette slot. This means that the T-72 can fire up to 12 different types of ammunition with different ballistics, and switch between them at the flick of two switches.


Unlike the handgrips for the fire control systems of previous Soviet tanks, the handgrips are permanently attached to the TPD-K1 sight. The handgrips have a protruding ledge at the base for the gunner's hands to rest on, and each handgrip has two buttons each. The left trigger button is for firing the co-axial machine gun and the left thumb button is resetting the laser rangefinder. The right trigger button is for firing the main cannon, and the right thumb button is for firing off the laser rangefinder. An ex tanker has remarked to the author that he found it difficult to operate the handgrips sometimes as it was rather confusing for him. He had previously operated a T-55 tank, and the thumb buttons were for firing the cannon and co-ax. With the T-72, the trigger buttons had not only moved, two more buttons were added!The price of progress is high indeed.




NIGHT SIGHTS


TPN-1-49-23





The TPN-1-49-23 is the gunner's night sight in the T-72 Ural and its variants, as well as almost all exported T-72 variants with the exception of the T-72S. The TPN-1-49-23 can be used in the passive image intensification mode or in the active infrared imaging mode, whereby infrared light emitted from the L-2AG "Luna-2" IR spotlight is used to illuminate the target. The "Luna-2" spotlight is mounted co-axially to the main gun so that all three devices - sights, cannon and spotlight - are adequately aligned. Like the commander's OU-3GA spotlight, the "Luna-2" spotlight is a simple tungsten filament lamp with a simple IR filter fitted in front of the bulb. Removing the filter transforms the IR spotlight into a regular white light spotlight. For passive observation, the sight is equipped with a 1st generation image intensifier tube. The image resolution is low, and the amplification factor is not high, so reliably seeing and identifying targets is very difficult in low light conditions. The inherent shortcomings of the 1st Generation system can be partially overcome with artillery-launched illumination rounds, but the low image resolution remains an issue.

Like the main sight, the TPN-1-49-23 is protected by a square-shaped armoured housing, with a bolt-on steel cover for the aperture. Beside the aperture is a single FG-125 infrared light, which is used only as a driving light and not for the TPN-1-49-23.




The sight has a maximum viewing distance of around 800 m in the active mode using the "Luna-2" IR spotlight. The passive image intensifier mode allows the same type of target to be spotted at ranges of up to 500 m if the ambient light is no less than 0.005 lux, which is the typical brightness of a moonless, starlit night with clear skies. Clarity and spotting distance improves with increasing brightness. Based on research into other 1st Generation night vision systems, the identification distance may be expanded to around 1000 m on moonlit nights, and it should be possible to spot tanks at distances of more than 1300 m during dark twilight hours, although low magnification and mediocre resolution complicates target observation beyond that range. The sensitivity of the image intensifier in the sight should be decreased to provide better image quality during twilight hours.

Soviet enthusiasm for image intensification technology gave the T-64 and T-72 a significant night fighting advantage over their Western counterparts, which relied solely on IR illumination technology for the entirety of the 60's and for most of the 70's. Case in point: The M60 received an image intensifier sight - a so-called "starlight scope" - only in 1977 with the M60A1 Passive modernization, and the original 1978 production M60A3 had the same passive nightsight. However, these new passive optics offered better performance than their contemporary Soviet counterparts, and the large investments in thermal imaging technology in the U.S allowed them to leapfrog over the USSR in night fighting technology by the late 70's. This is best exemplified by the use of AN/VSG-2 thermal imaging sights in the M60A3 (TTS) in 1979. The T-72A was introduced in the same year, but it still had the same TPN-1-49-23 night sight, and only upgraded to the TPN3-49 after some time into its production run, possibly at the turn of the decade.

Due to the short range of vision, the markings in the viewfinder of the TPN-1-49-23 are greatly simplified. All four ammunition types (including the co-axial machine gun) were represented on the markings, albeit not with complete exactness, but it was acceptable due to the short aiming distances expected. It's worth noting that the flat trajectory of subcaliber rounds like 3BM9 and 3BM15 made it infeasible to include them in the same set of markings as the other ammunition types, but their high muzzle velocity meant that it was fairly easy to hit a tank-sized target at short range anyway.




The end point of each line is an indicator for a certain distance for certain types of ammunition. A breakdown of the markings can be seen in the diagram below. This diagram is printed on an instruction panel on the sight itself, in case the gunner forgets the meaning of the markings in the heat of battle. As you can see in the diagram, the topmost point represents 100 meters for HE-Frag rounds and the co-ax, 200 meters for HEAT rounds, and 1100 meters for subcaliber rounds. To fire subcaliber rounds at targets below 1100 meters, the gunner would have to aim above the topmost point.




It has been frequently noted in various websites that the T-72 can be distinguished from the T-64 by the change in position of the spotlight from the left side of the cannon to the right side. This change was not arbitrary; the spotlight was placed next to the co-axial machine gun port so that the driver was physically blocked from sticking his head out of the hatch and in front of the machine gun when driving the tank during road marches, and so that the driver does not have to be in front of the machine gun when entering and exiting his station. Although accidental discharge was unlikely, there were some tragic cases, so the relocation of the spotlight was a serious safety consideration.




The sight cannot be used in daytime, because sunlight will overload the sight unit and possibly damage it. In accordance with this rule, the aperture has internal shutters linked to the firing trigger of the gunner's control handle. Upon firing, the shutters automatically close to shield the unit from the intense flash of cannon fire at night.




TPN3-49




Most T-72B1 tanks and some late model T-72As have the TPN3-49 night sight installed. The TPN3-49 exists as a substitute for the 1K13-49 in the case of the T-72B1, and it exists as an upgrade over the TPN-1-49-23 for the T-72A. The photo above, taken from "T-72: Yesterday, Today, Tomorrow" by Sergey Suvorov, shows the gunner's station in a mock T-72A (imitator for training) with the TPN3-49 installed. TPN3-49 is more advanced than its predecessor in many ways, but still retains many of the key features and drawbacks of its predecessor, including a lack of independent stabilization. Like before, the vertical stabilization system of the TPN3-49 is based on mechanical linkages connecting the mirror head in the sight to the stabilizer of the TPD-K1, thus allowing the gunner to maintain a fully stabilized field of view in combat and throughout the loading process of the cannon. One of the improvements of the TPN3-49 over the TPN-1-49-23 is the ability to switch between different viewfinder markings for different ammunition types, giving the gunner better aiming precision.




Instead of a single universal set of markings with predetermined aiming points, the TPN3-49 features comprehensive range scales and a range dial for each type of ammunition.

The new night sight features a more sensitive electron-optical converter tube and amplifier system, giving the gunner a brighter and clearer image when using the sight in the active night vision mode. Another improvement came from the installation of the newer L-4A "Luna-4" spotlight, which is more powerful than the older L-2AG "Luna-2" spotlight. The image intensifier in the TPN3-49 is improved, but still belongs to the 1st Generation, so the maximum viewing distance is only around 500-800 meters at an ambient light level of no less than 0.005 lux. This is rather poor compared to the "starlight scope" in the M60A1 and M60A3, which used a 2nd Generation image intensifier and offered a viewing distance of 1300 meters.

The L-4A spotlight can be distinguished from the L-2AG by the location of the power supply cable socket. The socket on the L-2AG was located on the right side of the spotlight, but the socket on the L-4A is located at the back, as you can see in the photo on the right. The photo on the left shows an L-2AG.




Even without delving into thermal imaging technology, the night fighting capabilities of the T-72A were still rather limited. In terms of active infrared imaging, the T-72 was behind both the M60A1 and the Chieftain. The M60A1 used the advanced AN/VSS-1 spotlight, featuring a motorized lens and occluder that enabled the gunner to remotely adjust beam width from 0.5-0.75 degrees in the narrow mode to 7 degrees in the wide mode as well as select between white light and infrared light on the fly. The AN/VSS-1 ran on 1 kW and had an output of 100 million candelas, but there was an overcharge mode that could bring the output up to 150 million candelas for a short time. Additionally, the M32 IR night sight installed in the M60A1 had an 8x magnification, giving the gunner better long range visibility compared to any T-72. The Chieftain was in a similar position of advantage, as it had an immensely powerful 2 kW spotlight with a large 570mm aperture, which greatly benefited the gunner in searching and engaging targets at longer ranges. The L-4A "Luna-4" spotlight is underwhelming in comparison, seeing as the spotlight ran on just 600 W and had an output of only 30 million candelas. Additionally, the beam width from "Luna" was fixed at around 1 degree, making it exceptionally difficult to search for targets across open terrain. Furthermore, the lack of an occluder, otherwise known as a blackout shield, in front of the xenon arc lamp in "Luna-4" meant that only a part of the light was directed from the concave reflector. The rest of the light was emitted forward, illuminating the tank itself as well as the ground in front of it, making the T-72 an extremely prominent target once the spotlight was activated.




Despite these drawbacks, the TPN3-49 apparently allows a T-72A gunner to spot a target at a range of 1300 meters in the active infrared imaging mode. This is surprising when we consider the fact that the reported viewing distance for the gunner of a Chieftain Mark. 3 is only 1000 meters, although that might be due to the relatively low 3x magnification of the Chieftain's No.33 IR night sight.


1K13-49





The 1K13-49 sight was created as a part of the guidance for new 125mm gun-launched missiles, but the new sight was also made with improved night vision capabilities using technologies derive from the TPN3-49 sight. The modulator and signal generator for the missile guidance system is in a separate box, but the laser emitter is installed inside the 1K13-49 sight itself. The maximum range of guidance is 4000 m.

The sight has a daytime channel that is normally used in conjunction with guided missiles, but having a daytime channel allows the 1K13-49 to be be used as a backup sight in case the TPD-K1 is non-functional. With a fixed 8x magnification in the daytime channel, the 1K13-49 can be an adequate replacement for the TPD-K1, but lacks a laser rangefinder and proper range scales for different ammunition types. The gunner is forced to make the most of the simplified markings provided in the viewfinder. The photo below shows the viewfinder for a variant of the 1K13 used in the BMP-3, so it may not be entirely accurate.




Its active infrared optoelectronic imaging system is also improved over the TPN-1-49-23. Now, the viewing range in the active mode is increased to 1200 m, though the image intensification system has not been improved, meaning that the 1K13-49 sight still only has an 800 m viewing distance (under ambient lighting conditions of no less than 0.005 lux). The optical magnification factor remains at 5.5x, like previous sights.

The diagrams below show the markings in the viewfinder for the night vision mode. The same viewfinder is used for both the active and passive modes of operation. Like in previous night sights, the chevron and range indicator lines are adjusted up and down while the range scale remains static. To adjust for longer distances, the range indicator line is adjusted down until it lines up with the desired range, and the chevron will also drop down by the same amount. By laying the chevron onto the target, the gun is elevated by the necessary superelevation and the gunner can open fire.




The sight has a field of view of 5 degrees in the daylight setting or 6°4' in the nighttime setting. It is independently stabilized in the vertical plane, with +20° elevation -7° depression.




As usual, the sight aperture has two protective housings; one enclosing the sensitive optical workings of the aperture itself with a tempered glass window and a shock-proof shell, and another very heavy duty steel carapace covering that, along with a thick steel window shield.




Externally, the key differences between the 1K13-49 and the other night sights lie in its distinctly larger armoured housing, complete with a remotely opened armoured shield.



1A40-4 Sighting Complex, SOSNA-U






SOSNA-U is a multi-channel thermal imaging sighting complex with capabilities matching those of its contemporaries, giving the T-72 a much needed boost in target acquisition and engagement capabilities. SOSNA-U uses the French-designed 2nd generation Catherine-FC thermal imager. The SOSNA-U sighting complex features an internal ballistic computer that enables it to automatically detect targets, track them, and calculate a ballistic solution including lead using the data from its internal rangefinder, its image processing software and its internal gyroscope (to calculate cant). As you would expect, the sight is stabilized in two planes. The sight has a very limited 3x optical magnification with an equally disappointing 6x maximum digital magnification. Contemporary thermal imaging sights are typically capable of very high digital zoom with double digit magnification factors.


The sighting unit can be seen in the photos below.





The view through the eyepiece in the optical day channel can be seen below.




SOSNA-U can reportedly be used to identify and engage tank-type targets at a nominal distance of 5 km in daytime in the normal optical channel, and up to 3.5 km in either day or night through the thermal imaging channel, but this is extremely optimistic. For one, there is hardly any location that is flat and featureless enough that tanks can be spotted at such a distance, assuming that the weather is clear enough that tank-sized targets can be distinguished from the terrain. The 3x optical zoom of the sight is simply insufficient for anything more demanding than general observation. It is just not possible to spot and identify a tank-type target at 5 km through the daytime optical channel. Secondly, the limited 6x digital zoom of SOSNA-U makes it very difficult for the gunner to identify even a halfheartedly camouflaged tank at the claimed 3.5 km distance. When looking through the thermal imaging channel, any vehicle will appear more as a white blob on the screen at such long distances.

Like the 1K13-49 sight it replaces, SOSNA-U has a missile guidance unit that allows it to be used to guide existing gun-launched missiles as well as newly developed missiles. The automatic target tracking feature of the sighting complex would be quite beneficial when engaging moving targets with guided missiles.


The gunner has two means of looking through SOSNA-U - the eyepiece, which is for the right eye and comes with a very comfortable forehead pad, and the 640x480px (5.7 inch) flatscreen display.




In addition to the sight itself, the T-72B3 upgrade also comes with a new digital ballistic computer of unknown make, as seen below. The sight itself cannot accept data from peripherals such as anemometers, thermometers, muzzle reference sensors, and so on, so in order to make use of such data, a ballistic computer is necessary. The addition of a digital ballistic computer elevates the fire control system of the T-72B3 up to a level on par with, and quite possibly exceeding the T-90A. The addition of the flatscreen display and the digital ballistic computer eliminates the possibility of stowing ammunition in the turret on the wall behind the gunner, as the gunner's master control panel is now moved to a spot behind his left shoulder, and the ballistic computer housing occupies quite a lot of space behind his seat.


The SOSNA-U is considered the de facto main sight for a T-72B3 gunners, relegating the TPD-K1 to the back-up role instead. The UVBU lead calculator device installed parallel to the TPD-K1M sight has been removed as it is now totally obsolete, thus retrograding the 1A40-1 sighting complex into the 1A40. Unfortunately, the designers apparently didn't see it fit to swap the placement of these two sighting units, resulting in less than optimal placement of the SOSNA-U, which is only somewhat negated by the use of a separate flatscreen display. Another rather strange quirk is that the sight aperture window cover has to be manually opened by unbolting it, which seems to be a step backwards from the 1K13-49.




Also note the IR lamp mounted next to the sight housing. As SOSNA-U is a thermal imaging sight, this lamp is totally unrelated to its operation. To the contrary, this lamp is used to replace the normal driving headlights if they are submerged under water or plastered with mud, which could happen if the tank is fording a stream or driving through a swamp. This lamp is turned on and off by the commander.




STABILIZERS



Stabilizer precision and sensitivity is a crucial factor in overall engagement capabilities, especially when on the move. In a continuation of the endearing Russian tradition of naming military hardware after innocent, peaceful things, the stabilizers are named after flowers. The hydraulic pump and power supply system are located in the hull, while the electric motor for turret traversal is at the turret ring in front of the gunner, behind the sights.

Turning on the stabilizer is done with the central toggle switch located just above the handgrips on the TPD-K1 sight. A well trained gunner would know not to keep the stabilizers on for too long, as it will overheat and wear out quickly.


2E28M "Sireneviy" (Lilac) Electric/Hydroelectric Stabilizer


The 2E28M dual-axis stabilizer is used in the T-72 Ural. The precision offered by this stabilizer is technically quite high, but holistically the weapons system is still too imprecise to guarantee hits on the move at very long ranges. Nevertheless, the high precision of "Sireneviy" is extremely valuable for its ability to automatically lay the gun on any given target quickly and precisely on short stops. It enables the tank to engage tank-type targets at average European combat distances or 1.5 km in a static position and on slow crawls with a reasonable degree of accuracy.

The stabilizer has two modes of operation: automatic and semi-automatic. The automatic mode is the primary mode for combat purposes; the stabilizer is at full operational capacity and will keep the gun aimed with maximum precision at the target when the tank is in motion. This mode is the default mode during combat, and is used when firing from all positions - stationary, while moving, and during short halts. The semi-automatic mode is an auxiliary operating mode as well as an emergency mode in the event of stabilizer failure. The stabilizer is set to this mode when combat is imminent in order to prevent overheating and to maximize the operating life of the stabilizer. In this mode, the vertical stabilizer system is disabled, so gun elevation reverts to a manual status, but the powered turret traverse and stabilization system remains operating, albeit at a reduced capacity; gun laying precision is greatly reduced, but the turret rotation speed is slightly increased. The semi-automatic mode is suitable when when the tank is stationary, or for firing during short halts. The slightly increased maximum turret traverse rate in the semi-automatic mode is ideal for tracking moving targets when the tank is in a stationary defensive position. In such conditions, the lack of powered gun elevation is not an issue.

The stabilizer is turned off entirely when combat is not expected, and the time needed to get the stabilizer to operational condition is 2 minutes. The stabilizer can remain activated for a maximum period of four hours, regardless of whether the tank is in combat or not.

The screenshot below (screenshot taken from this video) shows the location of some of the stabilizer components at the top left corner.





One of the components visible in the screenshot above is the gyroscope unit for the stabilizer.




Using this stabilizer, the turret is somewhat slow to turn at only 18° per second. It would take it a minimum of 20 seconds to do a complete 360° revolution. This has the effect of inhibiting the T-72's ability to react to the unexpected emergence of a dangerous target from different directions at close range. In the semi-automatic mode, the rate of rotation is increased to 20° per second, but this less irrelevant in combat because the semi-automatic mode is only used during road marches when combat is imminent, and not actually during combat. The traverse speed does not change from the minimum to the maximum rates smoothly. The turret traverse rate can be changed smoothly in the range of between 0.07° per second and 6° per second, but the transition to the maximum traverse rate of 18° or 20° per second occurs abruptly when the gunner turns his control handles to the maximum extent.

As usual, the stabilizer system revolves around the use of a pair of gyrostabilizers to measuring angular velocities in order to enforce corrections. Turret traverse is done electrically while gun elevation is accomplished using a hydraulic actuator. The hydraulic pump for powering the cannon elevation system is located under the cannon's breechblock, and the electric motor for turret traverse is installed in front of the gunner, behind his TPD-K1 sight unit.

An inherent shortcoming of hydraulic components is the heightened risk of an internal fire in the event of a full turret perforation. Hydraulic fluid is highly flammable, and it would most likely cause and spread an internal fire very quickly. This is an especially serious concern to the T-72, since it has numerous shells in loose storage which can accidentally detonate from uncontrolled fires.

The hydraulic fluid used is MGE-10A, a type of mineral hydraulic oil with very low temperature sensitivity, having an operating range of between -65°C to 75°C. The entire system operates at 7.25 psi. This is quite dangerous, as with all hydraulic systems, because hydraulic oil may spurt out from burst tubes at high speeds, spraying large portions of the interior with the flammable liquid.



Automatic mode:

Vertical:

Maximum Cannon Elevating Speed: 3.5° per second
Minimum Cannon Elevating Speed: 0.05° per second


Horizontal:

Maximum Turret Traverse Speed: 18° per second
Maximum Precise Turret Traverse Speed: 6° per second
Minimum Precise Turret Traverse Speed: 0.07° per second


Semi-automatic mode:


Horizontal:

Maximum Turret Traverse Speed: 20° per second
Maximum Precise Turret Traverse Speed: 6° per second
Minimum Precise Turret Traverse Speed: 0.3° per second



Average time taken for complete rotation: 20 seconds


For a minimum traverse and elevation speed of 0.05° per second, the stabilizer should have an accuracy of 0.88 mils, equivalent to a stabilization accuracy (not mean deviation) of 0.88 meters at 1000 m. The speed of turret rotation is reasonable enough by Soviet standards, considering that earlier tanks like the T-55 were not very good. The turret of a T-55 with a "Tsyklon" stabilizer could spin around at 15 degrees per second, and the turret of a T-62 could do 16 degrees per second. Sirenevny is an improvement over earlier stabilizers in every possible way.

Combined, all of the components belonging to the stabilization system weigh a sum total of 319 kg, including the working fluid (hydraulic fluid). On average, the stabilizer system consumes 3.5 kW of power.




2E42-2 "Zhasmin" (Jasmine) Hybrid Electro-Hydromechanical Stabilizer


Hydraulic pump, relay box and high-precision electric motor, from left to right.

The 2E42-2 is a conventional stabilizer system as it combines an electric turret traverse and stabilization drive with a hydraulic gun elevation and stabilization drive. The T-72B obr. 1985 began life in 1985 with this stabilizer. 2E42-2 was first used on the T-72A in 1984, but this model of the T-72A is difficult to distinguish from the T-72B obr. 1985 and is often labelled as the T-72B obr. 1984 for convenience. This stabilizer is not more precise than the "Sireneviy".

The T-72B obr. 1989 manual states that the maximum turret traverse speed is 16-24° per second, and mentions that the traverse speed when the target designation function is used by the commander is 16° per second. A rate of rotation of 24° per second is achieved under the "overcharge" condition. The gunner can get the turret to turn at this rate by turning his handgrips hard until it cannot physically go any further. The average power consumed by the stabilizer system is still the same as the 2E28M at 3.5 kW. The 2E42-2 has the same two operating modes as the 2E28M and previous Soviet tank gun stabilizers: automatic and semi-automatic.


Automatic mode:

Vertical:

Maximum elevating speed: 3.5° per second
Minimum elevating speed: 0.05° per second


Horizontal:

Maximum Turret Traverse Speed: 16-24° per second
Maximum Precise Turret Traverse Speed: 3° per second
Minimum Precise Turret Traverse Speed: 0.07° per second


Semi-automatic mode:

Horizontal:

Maximum Turret Traverse Speed: 16° per second
Maximum Precise Turret Traverse Speed: 6° per second
Minimum Precise Turret Traverse Speed: 0.3° per second


The turret traverse speed is improved to 24 degrees per second, enabling the turret to complete a full 360° rotation in just 15 seconds.



2E42-4 "Zhasmin" Electric/Hydroelectric Stabilizer


The 2E42-4 two-axis stabilizer is an improved modification of the 2E42-2 first used in the T-90. The 2E42-4 is installed in the T-72B3 and includes a much more powerful horizontal drive for faster turret rotation. According to Sergey Suvorov in "T-90: First Serial Tank of Russia", the 2E42-4 for the T-90 has an average stabilization accuracy of 0.4 mils in the vertical plane and 0.6 mils in the horizontal plane.


The 2E42-4 stabilizer offers a huge weight reduction of 120 kg over the 2E42-2 stabilizer, for a total weight of 200 kg. This is mainly because of the design simplification of the hydraulic gun elevation drive, the improved turret traverse motor, and the usage of solid state electronics in the digitized control systems. The screenshot below gives us a good view of the hydraulic pump for the gun elevation drive. The pump is mounted below the breech, and connects to the hydraulic elevator piston seen in the upper right corner of the picture.





Screenshot taken from the RT Documentary show "Tanks Born in Russia (E5) Kirill’s girlfriend reveals her biggest secret" (link).



Vertical:

Maximum elevating speed: 3.5° per second
Minimum elevating speed: 0.05° per second


Horizontal:

Maximum turret slew speed: 40° per second
Minimum turret slew speed: 0.054° per second


The much faster turret traverse speed enables the turret to complete a full 360° rotation in 9 seconds.



MANUAL


Manual traverse and elevation is possible with all T-72 turrets through the use of two flywheels located behind the hand grips. There are two gear settings; coarse and precise. The former allows the turret to turn as fast as the gunner can work the flywheel, while the latter produces minute changes to the turret and gun's positioning. Gun laying with the manual traverse can be just as accurate as with stabilizers, if not more so given that extreme care is taken, though obviously much, much slower and nearly impossible to achieve on the move. The gun elevation flywheel has a solenoid button for firing the main gun.






METEOROLOGICAL MAST



The T-72 first received a meteorological sensor unit with the T-72BA sub-variant. This manifested in the form of the DVE-BS unit, which can detect changes in wind speed and automatically register it in the ballistic computer. The maximum calculable winds speed is 25m/s. The information gathered is synchronized with the automatic lead calculation unit found in the 1A40-1 sighting complex. The T-72B2 and T-72B3 are also equipped with a DVE-BS unit.





D-81T CANNON




The T-72 is equipped with the 125mm smoothbore D-81T cannon, otherwise known as the 2A26 and the 2A46. It can fire a wide range of shells including; APFSDS, HEAT, HE-Frag, and even guided missiles beginning from the T-72B. The cannon weighs 2400 kg.

The cannon is partially derived from the U-5TS 115mm smoothbore gun, and the evidence of this heritage can be found upon close inspection. The recoiling mechanism is much more compact, which helps to reduce the volume of internal space taken up by the cannon in the small turret. Unlike the D-10T and U-5TS cannons, the recoil buffer is located at the bottom of the breech block rather than on top of it, so despite the larger caliber and mass of the cannon, it was possible to create a very low turret with a very steeply sloped roof while still affording the cannon the same range of vertical motion as in previous Soviet tanks.




2A26M-2



The original Obyekt. 172 and Obyekt 172M prototypes use the 2A26M-2 (D-81T), and earlier T-72 Ural tanks sported the 2A26M-2 as well. The 2A26M-2 is a modernized derivative of the 2A26 gun from the T-64A with appropriate modifications for the T-72. It had a barrel length of 6350mm, or 50.8 calibers. All variants of the 2A46 series had a barrel length of 6000mm, or 48 calibers. This is shorter than the 55-caliber 120mm British rifled L11 and L30 canons (6600mm) and shorter than the smoothbore Rheinmetall L/55 cannon (6600mm), but longer than the Rheinmetall L/44 (5280mm) cannon. One of the main problems encountered with the original 2A26M2 gun was reduced accuracy due to its excessive length and insufficient stiffness, and the lack of a thermal sleeve exacerbated the issue as the barrel easily warped from temperature differences. Also, the excessive length meant that oscillations at the muzzle had a greater amplitude, thus generating larger shot dispersion. The recoil buffer is installed asymmetrically, at the bottom right hand corner of the breech block, and the recuperator is installed directly underneath the breech block. The asymmetric installation of the recoil buffer resulted in the unbalanced motion of the cannon during its recoiling cycle while the shell is still in the barrel, and the unbalanced motion generated more intense oscillations at the muzzle, resulting in large shot dispersion. This configuration was carried over from the U-5TS gun.


The 2A26M2 cannon had an electroplated chrome lining but lacked a thermal sleeve and had generally poor longevity. The barrel had a life of a measly 600 EFC (Effective Full Charge). Replacing it was no easy task, either. The turret had to be lifted by a crane and positioned so that the gun assembly could be removed through the rear. This was a highly time consuming process that required specialized equipment. In the field, the crane would have been provided by recovery vehicles. In this regard, the Soviet tank industry was very much behind their Western counterparts. The 90mm gun on the M48 Patton, a 50's tank, already featured a quick change barrel. The 2A26M2 cannon had a rated maximum chamber pressure of 450 MPa. The photo below shows a T-72 Ural participating in exercises; notice the lack of a thermal shroud.






2A46





In 1970, the 2A46 was created as a modernization of the 2A26M cannon to rectify its most glaring issues. New technologies were mainly applied to the design and manufacturing of the barrel, but the rest of the cannon was not neglected. Various improvements increased the durability and accuracy of the new barrel, raising it to around 900 EFC. The maximum rated chamber pressure was not increased from the 2A26M2 and remained at 450 MPa, and the recoiling system remained essentially identical to the 2A26M2. The typical recoil stroke is 270mm to 320mm, and the maximum is 340mm. To manually open the breech, the commander has to pull on the breech opening handle in a single stroke, which is not easy as the pull weight of the handle is 75 kg.




According to "Increasing Firing Accuracy of 2A46 Tank Cannon Built-in T-72 MBT", 81% of 3BM-15 APFSDS shots fired from an unmodified 2A46 cannon will land within 0.5 meters of the aiming point in the vertical axis at a distance of 1 km, and 43% will land within 0.5 meters of the aiming point in the horizontal axis at the same distance. The probability of hitting a T-72 tank target at a distance of 2 km is 57%. Keep in mind that this is the mechanical accuracy of the cannon alone. Errors from the fire control system of the T-72 tank will most definitely increase the dispersion of shots.


Since the T-72M is the export modification of the T-72 Ural, one would expect it to mount the 2A26M2 cannon like its domestic counterpart, but it is difficult to verify this, because the presence of a thermal shroud on the barrel is not a reliable way to differentiate a 2A26M-2 from a 2A46. The photo below is a good example of this; the tank is a T-72M, since the turret is clearly the plain cast steel turret of the T-72 Ural (no composite insert) and the flip-out side armour panels are visible, but the barrel has a thermal shroud.




This photo and this photo both show the same configuration. The tanks are clearly T-72M models, but the barrels are equipped with a thermal shroud. The strongest evidence comes from "The Soviet T-72 Tank Performance", where on page 19, the specifications of the T-72M are given, and the 2A46 is listed as the main gun. From this, it is possible that the T-72M used the 2A46 since it began production, making it very likely that the design of the T-72M is a mixture of elements of both the Ural and Ural-1. Depending on the manufacturer, a T-72M may not be exactly the same as another.

The T-72A began its service life in 1979 with the 2A46, and the T-72M1 export model also used the 2A46. Several years later, the 2A46 was replaced by the newer and more accurate 2A46M, but its service life did not end there. The 2A46 was reverse engineered by the Chinese and a slightly modified copy of the gun is currently in production to equip the current generation of Chinese main battle tanks, including the Type 96, Type 99 and even the latest VT-4. A video of the assembly of a Chinese 2A46 is available on YouTube as part of a documentary on the VT-4. With that in mind, the screenshots below, taken from the video, shows - for all intents and purposes - a disassembled 2A46.







2A46M



In 1974, NII Stali mastered several advanced material processing technologies, which were subsequently transferred to the production of new cannons. These new technologies included electroslag remelting, differential isothermal quenching and improved thermomechanical processing. When the decision to modernize 125mm tank cannons was made in the late 70's, these technologies were implemented into the 2A46M cannon, among other things. According to Mikhail Baryatinsky, new T-72A tanks from 1981 onward were produced with the 2A46M. The 2A46M came installed with the T-72B since its introduction in 1984.

The barrel life was substantially improved by the use of a new, more durable chrome lining to reduce wear from new high-energy APFSDS shells. Thanks to the new chrome lining, the barrel life was increased to 1200 EFC. Accuracy was improved by a very impressive 50% due to the completely revised recoil system. The photo below (credit to Dmitry Derevyankin) shows the symmetric installation of two recoil buffers at the top right and bottom left corners of the breech block, and the retention of the recuperator at its original position directly underneath the breech. The symmetrical installation of two smaller recoil buffers greatly reduces the moment (the turning effect of a force) experienced by the cannon during the recoiling cycle, and thus reduces the oscillations at the muzzle while the shell is still in the barrel. The 2A46M has a typical recoil stroke of 260mm to 300mm, and a maximum recoil stroke of 310mm.


The cannon in the photo below is actually a 2A46M-1 for the T-64BV/80BV, but the breech block is otherwise identical to the 2A46M. The only differences are in the shape of the breech guards and in the presence of an electric motor for raising and lowering the shell casing stub ejection mechanism.




Furthermore, the method of seating the barrel to the gun cradle was changed. According to a marketing presentation by UVZ, the seating of the barrel was changed from the combination of the breech ring and support from a single contact point with the cradle to purely cradle support with two contact points.




Assuming that the increase in the mechanical accuracy of the 2A46M over the 2A46 is indeed 50%, then the probability of a 3BM-15 round fired from the 2A46M hitting a T-72 tank at 2 km would be 85.5%, if all other conditions are equal.

The 2A46M was also a milestone product in another way: the new mounting system for the barrel enabled quick replacement in the field from the outside of the turret by pulling it out from the front, without needing to remove or shift the turret. The procedure reportedly takes around 2 hours, but it is not clear if this is for an operation done in a depot or in the field. The maximum rated chamber pressure was increased to 500 MPa in accordance with the appearance of high energy APFSDS shells. Due to the relocation of the recoil buffers, the manual breech opening mechanism was redesigned, but remained principally identical. The oil level in the recoil buffers and recuperator can be checked without the opening of the stopper caps, making it much simpler and quicker to perform routine maintenance on the gun. Previously, tank crews referred to a schedule to record and determine if the buffer and recuperator in the 2A46 required a top up. If that information is not available, then the cannon would need to be retrieved from the turret and it would have to be inspected on a testing mount and tested with a pullback winch.

The overhaul of the design of the cannon also brought improvements to some of its less major components. Most notably, the manual breech opening mechanism at the top left corner of the receiver had to be redesigned because of the location of the new recoil buffers. The new mechanism has a ratchet, so that two tugs on the lever are needed, but the pull weight for the lever was decreased from 75 kg for a single tug to 25 kg in two tugs. This makes it much easier to work on the cannon within the confines of the tank. All of the modifications increased the mass of the cannon negligibly to 2.5 tons.




2A46M-5





The T-72B3 builds upon the T-72B with the inclusion of the 2A46M-5 gun (D-81TM-5), which was first introduced in 2005 and used in the T-90A. The 2A46M-5 can be considered the most perfect of the entire series thus far.


The dynamic balancing of the barrel during the firing procedure (while the shell is still in the barrel) have been better tuned, thus minimizing oscillations at the muzzle. The barrel itself was improved, now having 11% greater rigidity than the 2A46M barrel. The final result is a further reduction in shot dispersion. The maximum rated pressure in the barrel was increased to 608 MPa. According to the manufacturer, dispersion of all shell types by an average of 15% to 20%, and the accuracy when firing on the move has been increased 1.7 times, thanks to the greatly decreased vibration of the gun the tank is in motion over rough ground. Overall, the estimated probability of hit in combat was increased by 20-29% for APFSDS ammunition, 4-12% for HEAT ammunition, and 21-38% for HE-Frag ammunition.

The 2A46M-5 follows the 2A46M with the inclusion of a quick-replacement barrel. Like before, the barrel is released from the gun chamber and receiver assembly by twisting it by 45 degrees fitting a special hexagonal wrench on a hexagonal part of the barrel. The threads that lock the barrel to the receiver are seen in the screenshot below, taken from a news tour on the No. 9 Factory which builds these guns.




As you can see in the photo below, the location of the recoiling mechanism elements remained unchanged from the 2A46M. The main differences were not so obvious. More photos of the 2A46M-5 are available on Stefan Kotsch's website.




The drawing below (from here) showcases the location of the recoil buffers and the recuperator in relation to the axis of the cannon barrel. The drawing is probably valid for the 2A46M as well.




Furthermore, the 2A46M-5 is provisioned with special notches at the muzzle of the barrel, which are used for boresighting. Using the sights, the gunner aligns special markings to the notches and calibrates the sights to the gun from the recorded angle; a process that takes only 1 minute. It is presumed that this is only possible in the T-72B3 using the Sosna-U sights as the TPD-K1 lacks independent horizontal movement.


The gun can elevate +14 degrees and depress -6 degrees when facing the front, but elevate +17 degrees and depress only -3 degrees when facing the rear, with the engine compartment in the way. This is generally sufficient for cross-country driving with lots of minor dips, dives and bumps, but the T-72 is unable to fully take advantage of certain hills for hull-down shooting, but it is free to take cover behind mounds, rocky outcrops, or maybe in a self-made tank hole dug into the ground. The lackluster gun depression as compared to NATO tanks can become an issue in highly irregular terrain. Compared to previous Soviet tanks, the gun depression of the T-72 is slightly better than average.

All of the D-81T cannons have a normal recoil stroke of between 300 to 340mm, more for the high-pressure APFSDS rounds and less for HEAT and HE-Frag rounds.


The end of the barrel has four shallow cuts in the shape of a cross.





This is for the gunner to align and tie two pieces of string into a crosshair over the end of the barrel for the purpose of zeroing the gun in the field. The photo below shows the gunner of a T-72B doing this during a snap exercise.

(Photo from Ministry of Defence of the Russian Federation)




Here is another photo:




Worn out barrels tend to exhibit worse accuracy. This was especially noticeable during the war in Iraq, where Iraqi T-72s often urgently needed barrel replacements, because they had been used since the Iran-Iraq war. Because of the embargo on military equipment, they had no access to fresh barrels and they lacked the technology to produce their own. Firing APFSDS shells, especially the first generation ones that Iraq was supplied with (steel sabot with copper driving bands, and bore-riding projectile fins), was especially harsh on the barrel. The 2A28M2 cannons that Iraqi T-72Ms (analogues of T-72 Ural and Ural-1) and T-72M1s could only tolerate 160 to 170 of such APFSDS shells before becoming unsafe to fire. The 2A46M-2 on the T-72B could fire 220 contemporary APFSDS shells (high energy APFSDS), but the latest 2A46M-5 can let off at least 500 of the currently most common shells (3BM-44).





Needless to say, firing from a worn-out gun barrel can be very dangerous. Fracturing of the barrel is possible, but thankfully, the fuses of explosive ammunition like HE-Frag and HEAT shells exclude the possibility of premature detonation. Still, disintegrated fragments may potentially harm people and equipment in the vicinity.



AMMUNITION STOWAGE





 AUTOLOADER



The T-72 uses an AZ electromechanical carousel-type autoloader with a 22-round capacity. The autoloader was modernized in the T-72B to missiles to be carried. The new autoloader had higher reliability, and could also store longer and larger projectiles. We will examine the original Ural autoloader, and examine the newer T-72B autoloader in the context of improvements to the original. The patent for the T-72B autoloader (Russian Patent No. 2204776) is available hereAs mentioned earlier, the gunner controls the autoloader from a control unit located on the TPD-K1 sight.

Each shell and propellant charge stored within the carousel is housed within a two-tiered steel cassette with extended bills to properly line up the shell or propellant charge with the gun chamber. The diameter of the carousel spans the width of the hull. Being made from steel, the cassettes provide some meager protection for the ammunition.

Below, you can see the ammunition cassettes being dropped in place on a T-72B3 autoloader. You can also see the tank's escape hatch to the left of the photo. The metal arm protruding from the silver-coloured central hub is part of the emergency manual carousel rotation mechanism. The carousel rotates independently of the turret and the armoured bulkhead on top of it during both normal and manual operation.




The notch on the edge of the central hub marks where the tray lines up flush with the trapdoor on the carousel cover. The notch allows projectiles that are physically longer than the ammo cassette to pass through the trapdoor.

Here is a diagram of the ammo cassettes. The maximum length of each cassette is 680mm, just 2mm longer than the HEAT projectiles carried by the T-72 like the BK-14 and BK-18, and only 5mm longer than HE-Frag shells like the OF-19. The APFSDS ammunition employed in the USSR during the Cold War was the shortest among the three main ammunition types.




Modified cassettes are used in the T-72B carousel in order to accommodate guided missiles. The modified cassettes have special latches on both sides accommodate guided missiles and to prevent the stabilizing fins of the missile from accidentally deploying when the missile is violently rammed into the cannon.




While the new cassettes are designed to accommodate guided missiles, the length of the cassettes remain at 680mm, so the "Svir" guided missiles (695mm long) employed by the T-72B will overhang the cassette by 15mm.

The cassettes are arranged radially around the central hub.


The autoloading cycle requires the gun to be locked at a pre-programmed elevation of +3°30', which is done so automatically as the cycle begins. It is claimed in the memoirs of Leonid Kartsev that this was superior to the Kharkov T-64A as the spent shell stub was a significant source of propellant fumes from smoldering residue inside the stub, and that disposing of the stub reduced the concentration of fumes in the fighting compartment. There may be some truth to this claim, as video evidence has shown that even when there is virtually no escape of fumes from the cannon breech after firing (indicating that the fume extractor is working well), the spent shell stub may still pollute the fighting compartment until the propellant residue is completely burnt. This video is a good example of this. The immediate ejection of the stub would indeed be beneficial.

Steven J. Zaloga claims there were some problems with zeroing the sighting system and the cannon because the sight was independently stabilized, and the vertical stabilizer for the cannon would sometimes fail to synchronize with the stabilizer unit in the sight as the cannon resets to its original position when finishing its loading cycle. However, it is doubtful if this issue truly exists, because the stabilizer for the cannon is slaved to the independently stabilized TPD-K1 sight, so the stabilizer will always attempt to lay the cannon as close as possible to the aiming point of the sight. The alignment will never be perfect, because the weapons stabilizer is less precise than the stabilizer for the sight. Zaloga may have mistakenly labelled the small alignment error between the two cross-linked systems as a design flaw instead of a fundamental technical limitation.

During the reload cycle, a cassette is elevated to the ramming position, and the two-part ammunition is rammed into the gun breech. Because the cannon automatically elevates by +3°30' degrees at the beginning of the reload cycle, the top half of the autoloader elevator is slightly tilted to bring the cassette into alignment with the breech. The slight tilt is visible in the diagram below. The diagram shows a T-72 Ural type autoloader. The T-72B has a different carousel.




Shell casing stubs are automatically ejected by a stub catcher and ejector through a small port at the rear of the turret, visible below:




The stub catcher can be seen in the screenshot below (the perforated circular thing at the back has nothing to do with the stub catcher). It is possible for shell casing stubs to miss the stub catcher, although it is a rare occurrence.





MEMORY UNIT



The autoloader is able to recognize the position of each round stored in the carousel through the carousel storage memory unit, shown below. Three ammunition types can be indexed into the carousel.





To load ammunition into the autoloader, the commander must use his control box to cycle between cassettes. After loading a cassette, he must input the ammunition type into the memory unit by pushing one of three optional buttons, one for each type of shell: HEAT (K), APFSDS (B), or HE-Frag (O). He can then complete the loading procedure and cycle to the next tray.






The memory unit indexes the type of ammunition on a data disc stored inside the circular housing. The type of ammunition is identified by the system using a binary system on the data disc. There twelve radial magnetic rings on the surface of the disc divided into three groups and twenty two sectors. Four of the radial rings are for recording the type of ammunition, four are used to determine when to brake the carousel rotation motor, and four are used to determine where to stop the carousel in order to line up the ammunition to the trapdoor.


Recording the information is done by three current carrying pins, with interact with the magnetic rings via electrical contacts. Storing the information itself is done by changing the polarity of the magnetic spot to either positive or negative through the electrical contacts. The electrical contacts are kept in contact with the magnetic rings via small springs to ensure that reading the data is still possible even while the device is experiencing strong vibrations (such as when the tank is on the move over rough ground) or a shockwave from an explosive blast. However, the constant pressure wears out both the magnetic ring and the electrical contact over time leading to a loss in the ability to record and read data, and the metallic dust from the worn surfaces can contaminate other parts of the unit, causing reading errors. Such errors could prevent the autoloader from accepting new ammunition when reloaded, or cause the autoloader to lose track of where ammunition is stored or even to "forget" when to stop rotating the carousel if it is already in motion (so it rotates indefinitely). Even if the recording surfaces are not worn out, it is also possible for the device to fail from the accumulation of dust and grime over time. At this point, it is possible to either replace the electrical contacts the hard disc, or replace the entire memory unit.




The rotation of the data disc is not powered by an internal motor, but by the carousel itself via a crankshaft passing through the bottom of the memory unit. When the autoloader is activated by the gunner or commander initiating the reload, the carousel motor receives the command to rotate, but it does not know when to stop until the memory unit reaches the appropriate ammunition type, so if the gunner selects HEAT rounds, the carousel will rotate until the system reads the appropriate binary code on the data disc, whereupon the command to stop the carousel motor is given (which is also written on the data disc, as mentioned before).

In other words, the system does not know what the shortest route to the selected ammunition type is. This system limits the carousel to rotating in only one direction - the motor is capable of rotating in both directions, but due to the system limitations, the reverse rotation is only activated when braking the rotation of the carousel. After the round is loaded and the ammo cassette returns to the carousel, the memory unit rewrites the data to a null value (000) to represent the empty status of the cassette.

The design of the data disc is clearly an extremely simple and archaic form of a hard disc storage with an extremely low storage capacity. The lack of sophistication, however, is completely justified by the lack of a need to store large volumes of data and the high robustness required of the system. The simple design of the memory unit grants high resistance to shock and mechanical damage, and its self contained housing facilitates quick replacement if it is damaged. The most common source of autoloader malfunctions is the memory unit.



Due to the limit of three ammunition types, this memory unit is not used in the T-72B, as there is a new type of ammunition: guided missiles. According to the patent for the T-72B autoloader (Russian Patent No. 2204776), the memory storage was upgraded to accept a fourth ammunition type; missiles. The upgraded memory storage unit was also improved for better reliability.


The upgraded memory storage unit had a rotary dial instead of three buttons. The dial has four positions for the four ammunition types. To select and index an ammunition type, the dial is turned to one of the four positions, and then pressed. A closer look at the dial is available in this video at (3:08). The new memory unit can be seen in the screenshot below.





The photo below shows a T-72 Ural or T-72A, as evidenced by the welded appliqué armour plate on the upper glacis. Note the T-shaped box with wires coming out of it to the left of the blue torsion bars, at the center of where the carousel would be.





The T-shaped box is a VKU-330-4 power distribution unit to supply power to the tank turret. The VKU-330-4 is shown below.





The permissible length of projectiles in the T-72B autoloader carousel was increased by reducing the size of the central hub. This was done by redesigning the hub and replacing the VKU-330-4 power distribution unit installed on top of the carousel rotation motor with the VKU-1 unit. The photo below shows a T-72B3 with a VKU-1. Note the three protruding arms instead of a T-shape.





This modification enabled the 695mm-long "Svir" guided missile to be used with the carousel. The T-72B1 uses the Ural autoloader and memory system, as it is a low cost version of the T-72B without the missile firing capability.


In the T-90A autoloader, the system was revised and digitized. The information on the type and location of the ammunition in the carousel is stored digitally in a separate device, and the shortest distance to reach the ammunition is determined by an algorithm. The absence of the old disc-type memory unit is confirmed in the photo below, although the crankshaft housing from the carousel that would have rotated the hard disc is still present as a "vestigial tail" of sorts. This is evidence that although the control system was overhauled, the T-72B carousel was retained. The issue of two-way rotation is resolved by the implementation of a sufficiently sophisticated control system. The carousel rotation motor itself is reversible and has always been capable of both clockwise and anti-clockwise rotation since the original version in the T-72 Ural, but due to the rather crude ammunition retrieval system, the reverse function of the motor had only been used for braking until then.





There are some claims that the T-72B3 uses the autoloader from the T-90A, and that this allows the T-72B3 to use more elongated APFSDS rounds. Currently available evidence shows that this is almost completely incorrect. A T-72B3 with the old T-72B memory unit (Red) and commander's control box (Yellow) can be see in the photo below.






This shows that the ammunition indexing and retrieval system is still based on the older T-72B, so the carousel must also be from the T-72B. However, it is clear that the system has been revised. Note that the old ammunition selector dial has been replaced with a new one. The photo below - this time showing the T-72B memory unit (Red) in a T-72B3 obr. 2016 - supports this theory. Even in 2016, the T-72B3 is evidently still using the old T-72B carousel, and even the same control box (Yellow) is used.






Another piece of evidence showing that the T-72B3 uses elements of the T-90 autoloader is the fact that the stub ejection port hatch momentarily opens and closes immediately after firing without actually ejecting a shell casing stub, presumably to evacuate the fumes. This is feature first seen in the T-90, and displayed in this videothis video and this video and many others. The fact that the T-72B3 also has this feature indicates that it shares something in common with the T-90 autoloader. Whether the T-90 autoloader is capable of loading longer shells or not is still not clear, so it would be a little presumptuous to assume that the T-72B3 can. As we have seen, there is evidence to show that the T-72B autoloader can load longer projectiles than the Ural autoloader, but there is nothing concrete that indicates that there were any further upgrades to projectile length after the T-72B. It is often assumed that the carousel is to blame for the limited projectile length, there is evidence that the carousel has no part in this limitation.

In June 2005, a patent (Patent No. 2300722) filed by UKBTM for a method of increasing the permissible length of projectiles usable in the autoloader was filed. The patent describes a modified autoloader elevator design wherein the ammo cassette is pulled backward to avoid the cannon breech as it is elevated to the ramming position. It is hinted in the patent that the main restriction on the projectile length is not the carousel, but the cannon. To be more specific, the patent states that a possible method of increasing the permissible length of projectiles involves moving the cannon forward, and that this would require significant reworking of the turret, and it would disrupt the balancing of the cannon. The carousel is not mentioned at all. It is not clear if this patented system was actually implemented in new production tanks or implemented at all, but since the carousel is not the main limiting factor, it is absolutely possible that the T-72B3 can simultaneously have the old T-72B carousel installed and still be able to fire the same shells as the T-90A. It is very likely that the patented autoloader modification was implemented in the new T-90M modernization, and not in any other T-72-pattern tank.



The photo below shows the location of the memory unit for the Ural and the carousel trapdoor through which the two-piece ammunition passes through.




This scan comes from the book "T-72/72M/72M1 in detail", from preview pictures available on super-hobby.com (link).


The time taken per loading cycle is around 7 seconds. This enables the tank to achieve a maximum rate of fire of 7 to 8 rounds per minute. The cyclogram below shows the chronological order of the steps in the autoloading process. The cyclogram gives a total loading time of around 7.7 seconds, but this is because the cyclogram includes the rotation of the carousel over two ammunition cassettes instead of transferring directly to the next one, probably to represent a randomized sorting arrangement of ammunition in the carousel or a change in ammunition types. The cyclogram also includes the firing and recoil of the cannon after the loading cycle, so the cyclogram can be considered to be representative of the maximum rate of fire of the T-72 with a mixed ammunition load, rather than the actual maximum rate.




As you can see in the cyclogram, the last second of the loading cycle is taken up by the release of the cannon from hydrolock and by the automatic laying of the cannon back into the last previous aiming position and then onto the new aiming point, so the gunner can open fire immediately, which is also represented by the tag "Recoil of the cannon", which represents the firing of the cannon immediately after loading is concluded. This is possible because of the independent vertical stabilization of the gunner's primary sight and the separation of the turret traverse system from the rotation system of the autoloader carousel, so he can conduct ranging and aim at a new target during the loading cycle. This is no different from any other modern fire control system. The biggest drawback of the AZ autoloader is that it requires two ramming cycles. Each ramming cycle takes 1.5 seconds, so if there were only one ramming cycle, the autoloading cycle would take less than 6 seconds, putting it on par with the 6ETs-15 "Korzina" autoloader used in the T-64A and T-80.


The AZ autoloader carousel is very compact, as you can see in the photo below. For some reason, there is a T-80 in the background. Based on this official UKBTM drawing of the cross-section of a T-72, the carousel occupies around half of the internal height of the hull, so its height is likely to be around 0.45 meters. Note that the carousel in the photo below lacks a memory/input unit, but has a cylinder attached to the central hub, indicating that this carousel is for a T-72B.




There is some additional equipment installed on top of the carousel cover. The silver box you see near the center of the carousel cover is a KR-175 relay box. It connects to the VKU-330-4 power distribution unit and supplies power to the turret.




The T-72 does not have a significant disadvantage when compared to human loaded counterparts, which include the majority of NATO tanks. Most examples can achieve a 4 to 5 second loading time - when their tank is immobile. However, it's a whole different story on rough terrain. An advantage to the autoloader is that a bumpy ride, change of direction or slope traversal will never affect the autoloader's operation in any way. It can maintain its normal cyclic loading rate in whatever condition or orientation the tank is in. In manually-loaded tanks, the whole vehicle will pitch and dive as it drives over ruts and mounds while the gun, which would be disconnected from the stabilization system in tanks like the Abrams when the loader drops the safety lever, will move up and down on its own volition, making it less straightforward for the loader to get the shell aligned with the chamber to ram it in.

Firing on the move is usually done at a low cruising speed or at a crawl in order to maximize accuracy, but a tank speeds up and performs evasive maneuvers in between shots in order to avoid enemy fire, before slowing down again to return fire. The stressful time between shots is when the loader must perform his duties, and it would be much, much harder to load the cannon during that time. This video illustrates this point perfectly. At 1:08 and 1:31 in the video, the movement of the gun delays the loader by around a second, extending his loading time to 7.9 seconds and 8.2 seconds respectively (loading time is defined as the time between dropping the loader's safety lever and moving back to a position away from the path of recoil). This would not be an issue for a tank furnished with an autoloader, but to be fair, this is also not an issue for tanks installed with a loader's assist system where the gun automatically raises by a few degrees and fixes the breech in detente, placing it at the optimum loading angle for the loader. The earliest tank to have this feature was the T-54B, followed by the T-62. Later on, tanks like the Leopard 2 and the Merkava 4 featured similar loader's assist systems.


The autoloader can maintain its cyclic loading speed throughout an extended engagement until the carousel is exhausted. A human loader, on the other hand, will be exhausted from long before the ammunition is exhausted or even before combat even commences, whether it be due to excessive heat, excessive cold, shortage of food, shortage of water, or anything else you can imagine. None of the crew members in a T-72 have to perform manual labour under duress.

All in all, the T-72's autoloader is entirely satisfactory for generating a sustainable rate of fire for realistic encounters. While NATO tanks with human loaders were intended to put out as many shots as possible on huge formations of approaching Soviet tanks while staying stationary behind cover, the T-72 never had such a requirement. In modern shoot-and-scoot combat where tanks rarely stop moving or risk getting hit themselves, the advantage of human loaders become much less apparent. In this sense, the T-72's autoloader is not a hindrance at all, but an advantage, if the system is not at least on par with its Western counterparts.

Having compared firing rate, it would be illogical to not also compare ammunition capacity, especially against the T-72's famous rivals; the Abrams and the Leopard. Surprising as it may be, the T-72 carries more ready ammunition; 22 in the carousel compared to 18 and 15 in the bustle ready racks of the Abrams and Leopard respectively. This is not an issue for any three of these tanks, because it is rare for a tank to expend so much ammunition in a single engagement. There is typically a lull in the fighting, which is when the loader in any tank would take the time to replenish his ready racks from the less convenient stowage racks. In the case of the T-72, the commander will replenish the carousel using the loose ammunition stowed on board the tank.



CAROUSEL PROTECTION


The overhead cover on top of the carousel acts as a false floor for the turrets' occupants. Here is a better view of the cover.




This close up of the surface of the autoloader carousel reveals that it is actually made of thin sheet steel, but it is covered in a layer of thick, rigid matting. The matting resembles the anti-radiation lining and cladding around the rest of the tank, so its purpose is likely to serve as radiation protection for the crew. However, the anti-radiation lining is known to be an effective spall liner, so it serves as additional protection as well. The anti-radiation lining carried over from the T-72 Ural to the T-72A, T-72B and the T-72B3, but was removed in the T-90 and compensated by thickening the cover. A good view of the matting is visible in the picture below (screenshot taken from TV Zvezda series "Made In the USSR", episode "T-72 Main Battle Tank").




The sheet steel cover is bent down at the edges for structural stiffness, so the cover you see in the screenshot above does not represent its true thickness.

The perimeter of the carousel is protected by sheet steel guards at certain places, as shown in the photo below. In other places, the perimeter of the carousel intersects with conformal fuel tanks. The thickness of the guards was increased for the T-72B autoloader. The original perimeter guards can be seen in the photo below (open image in new tab and zoom in). Note the two reinforcement ribs pressed in to the plate - this indicates that the plate is quite thin and flimsy.




This photo gives us a closer look at the guard. The sheet is really quite thin, so it is more likely that their main function is to help prevent unintentional interactions between the driver and the carousel. The ballistic protection of such a thin plate is questionable at best.




Here is another look at the sheet steel guard. Screenshot taken from TV Zvezda series "Made In the USSR", episode "T-72 Main Battle Tank".




In the T-72B, these ribbed steel guards were replaced with a thick solid plate, as seen in the photo below of a late model T-72B undergoing repairs at the 103rd Armoured Repair Plant in the Far East (photo credit to darkbear-ru). It is very unlikely that the tank in the photos below is a T-72B3 model because the delivery of the very first T-72B3 tanks only began in 2013, whereas the photos below were uploaded to darkbear-ru's livejournal in December 2012. Also, the tank has clearly seen some use, as shown by the worn rubber rims of the roadwheels.




The lower left corner of the screenshot below grants us a closer look at the steel guards for the T-72B3 carousel. It appears that the steel guard plate was not changed from the T-72B to the T-72B3.




The T-90A appears to have the same steel guard plate as the T-72B and T-72B3, as shown in the photo below (credit to twower). Note that there are two fire extinguisher canisters clipped to the guard plate. The same clips are seen in both of the photos of the T-72B and T-72B3, likely indicating that all three tanks have the same armoured plate installed in front of the carousel. The rather large gap seen in the photo below is only due to the top-down perspective of the photographer. When viewed horizontally, the armoured plate fully covers the carousel.




As T-72B-1 uses the autoloader of the T-72 Ural, it also retains the same steel guard, as proven in the picture below. Screenshot taken from a video by user Khercrit, titled "T-72: how a mechanic crawls into the turret". You can get an idea of how thin the sheet steel cover atop the carousel really is in the screenshot below.




The type of steel used for the perimeter guards are not known, but the thickness of the older T-72 Ural sheet steel guards would be insufficient. The thick plate in the T-72B can be considered a serious armoured plate, and would undoubtedly have a positive effect on the survivability of the tank. It is important to point out that we know that the guards are made from steel and not aluminium because we can observe rust on the surface of the sheets.

This article translated by Peter Samsonov details the post-penetration effects of 125mm APFSDS ammunition. The original pages of the Russian document were first shared on Andrei Tarasenko's blog. The document featured in the article pertains to a lethality analysis done on 3BM-9, 3BM-15, 3BM-22 and 3BM-26. These four rounds will all be examined more closely later on, but for now, it is only necessary to summarize that the 3BM-9 is an all-steel "torpedo" projectile, while the 3BM-15 and 3BM-22 are composite shells with a a tungsten carbide core at the front of the projectile, and the and 3BM-26 has a tungsten carbide core in its tail. All of the shots were for a 60 degree obliquity impact, and the velocity of all of the shells corresponds to their velocities at 2 km.

According to the article, the vast majority of fragments expelled behind the armour plate are smaller, low energy particles that are only capable of penetrating 3-6mm of aluminium sheeting at a distance of 0.5 to 1 meters. Keeping in mind that the overmatch factor used in the experiments was in the range of 100mm to 300mm, these figures simply cannot be considered realistic if the same or equivalent ammunition was fired at a T-72 tank, but assuming that a composite shell managed to overmatch the front hull armour of the T-72B by 100mm to 300mm, the fragments will definitely not be able to penetrate the steel guard around the perimeter of the carousel, especially not after passing through the anti-radiation lining (which doubles as a spall liner) lining the interior walls of the tank. This is important, because igniting or detonating ammunition requires a certain amount of energy. Very low energy fragments that can barely pierce a millimeter of steel would have no hope of igniting the ammunition, and more energetic fragments may lose enough energy from impacting the carousel perimeter guard that they may fail to ignite the ammunition. The thick armour plate in the T-72B may even be able to protect the carousel from fragments that are capable of penetrating 30mm of aluminium or more, of which there are comparatively few. It is not known what type of aluminium allow was used for the plates in the lethality analysis, but is is likely to be structual aluminium and not armour-grade aluminium. This is because the equipment in Soviet tanks (radios, control boxes, relay boxes, sights, etc.) is encased in a thick cast aluminium housing. We can safely say that the armoured plate, which appears to be around a centimeter thick, is equivalent to more than 30mm of structual aluminium.

It is worth mentioning that the inefficient composite construction of Soviet APFSDS rounds like the aforementioned four models makes them exceptionally prone to disintegration and fragmentation after passing through armour plates. Early 105mm APFSDS also relied on composite projectiles, but later on, more efficient long rod ammunition was deployed, and such ammunition would produce much fewer but much more powerful fragments given the same degree of overmatch. So unless the penetrator barely makes it through the armour of the tank, long rod ammunition has a much better chance of penetrating the armour plate around the carousel than composite penetrators, even if the composite penetrator achieves a greater degree of overmatch somehow. All in all, the chances of reaching - let alone igniting - the ammunition in the carousel is rather low, even in the event of a hull penetration. Fragments from a turret penetration would most likely fail to even reach the carousel.


In short, only the T-72 Ural and T-72A use the original autoloader and original carousel with minimal side protection. The T-72B used a different autoloader carousel with revised ammo cassettes in order to fit missiles, and the size of the central hub was reduced in order to fit projectiles that exceeded the length of the ammo cassettes. The armour protection for the carousel was also upgraded by installing a bona fide armoured plate in front of the carousel, behind the driver.


The carousel rotates independently of the turret. It can rotate to line up new shells at a speed of 70 degrees per second, but as mentioned before, it can only rotate in a counterclockwise direction. This needlessly prolonged the loading cycle in some circumstances, but it is entirely possible to avoid this issue by practicing smart ammo placement. If APFSDS ammunition is stowed to the right of HEAT ammunition, and HEAT ammunition is stowed to the right of HE-Frag ammunition, the time needed to load anti-armour rounds can be greatly reduced at the expense of greatly increasing the time taken to reach the HE-Frag rounds. This way, the gunner can start with APFSDS, and then switch to HEAT without delay when APFSDS is exhausted, or switch to HEAT quickly to deal with IFVs when the high priority tank targets have already been knocked out. Switching to HE-Frag from APFSDS takes longer, but if the target is supposed to be engaged with HE-Frag, then it can be assumed that it is not a high priority target like, say, a tank.

Here is a video of a demonstrator autoloader carousel spinning:




In the summer of 1969, a comprehensive test cycle conducted on a number of Object 172 tanks in Central Asia and in the South-Western regions of Russia revealed that the air purification system, engine cooling system, the autoloader and the T-64 suspension had insufficient reliability. These issues were partially eliminated on the subsequent batch of Object 172 tanks. Work on these tanks continued until February 1971, and by then, most of the subsystems in the tank were working within acceptable parameters. The reliability of the autoloader at that point was excellent, having a loading failure rate of only 1 per 448 loading cycles (Baryatinskiy 2010). This roughly corresponded with the barrel life of the 2A26M-2 cannon of 600 EFC. 600 EFC equates to 600 rounds of ammunition with an EFC rating of 1 like HE-Frag or HEAT, but harsher and high pressure APFSDS rounds which erode the barrel quicker have a higher EFC rating of 4 to 5. As such, the rule of thumb is that the autoloader should undergo maintenance or light repair work whenever the gun barrel is in need of replacement. Periodic inspections and testing would greatly benefit the longevity of the autoloader. The newer T-72B autoloader has improved reliability, but the magnitude of the improvement is not known. If troubleshooting is not successful or if individual components cannot be repaired from inside the tank, then the replacement of the entire carousel can be done in the field with the help of an engineering/recovery vehicle like the BREM-1 or at any garage with a hoist large enough to detach the turret. Replacing the rest of the autoloader requires the turret to be partially dismantled.


The gunner has a full set of autoloader controls for selecting ammunition to fire, or to replenish the autoloader. In order to fill up the autoloader, the loading process has to be reversed. According to the manual, reloading the carousel with a full stock of ammunition from an external supply of ammunition takes 4 to 5 minutes only.







LOOSE STOWAGE



Aside from the carousel itself, ammunition is stored in racks located throughout the interior of the tank in various nooks and crannies with varying degrees of accessibility. While much of the ammunition in stowed in fairly secure conformal fuel tanks, there are a few rounds of ammunition that are placed out in the open. For the T-72 Ural, 17 rounds are carried in loose stowage. The stowage layout in the T-72 Ural was carried over to the T-72A, but the layout was was revised in the T-72B, leading to an increase in the number of shells carried in loose stowage to 22. This enabled the tank to carry two full complements of ammunition into battle and fully reload the carousel in the absence of resupply trucks.


The stowage layout for the T-72 Ural and T-72A is presented in the diagram below. The diagram is from the T-72A manual.


The layout for the T-72B is shown in this diagram:





Almost all of the propellant charges - the most vulnerable half of the two-part ammunition - are stowed in cylindrical slots inside these conformal fuel tanks. There are twelve slots in the large fuel tank behind the autoloader carousel for propellant charges. Due to the excellent location, the charges are almost completely safe - the carousel would always be hit instead. A cross-section of the propellant charge slot in the fuel tank can be seen below.



The right hull fuel tank on the right hand side of the driver has slots for three propellant charges and four shells plus a single exposed propellant charge stowed in a circular cup at the back of the fuel tank. See the photo below.




A single propellant charge and shell is stowed on a clips on the left hand side of the driver; exposed, but still reasonably protected as it is behind the left hull fuel tank. This was changed so that three propellant charges are stowed instead in the T-72B.


Cross-sections of the slots for the shells in the conformal fuel tank are shown in the diagram below. The slots are designed with the dimensions of HE-Frag shells in mind, so they are large enough to accommodate the two other ammunition types, which were shorter, even the long rod APFSDS ammunition appearing late in the Cold War. The shells are held in place by a simple crescent shaped rotating cover.



The conformal fuel tank was modified in the T-72B and limited to only three.



More shells and propellant charges are stowed on top of the carousel cover. Some of the propellant charges and shells are clipped to the cover, and others are placed vertically and clipped to the turret ring. There is one position at the 11 o'clock sector of the carousel cover where a single shell can be clipped onto the cover lying down. This shell prevents the driver from moving to the gunner's position, or the gunner from pulling the driver out of the tank through the turret. Two propellant charges

The circular "ashtrays" at the back of the carousel at either side of the trapdoor are where the shells and propellant charges are placed upright. The shells are secured using clips attached to the turret ring. The "ashtrays" can be seen in the photo below, but the diagrams from the manuals are much more useful. It is shown that two pairs of shells and propellant charges are stowed to the left of the carousel trapdoor, behind the backrest of the commander's seat.





The two pairs of shells and propellant charges stowed on the racks on the carousel cover are located behind the commander's seat. The clips that secure them to the turret ring can be seen in The Challenger's video review of a Czechoslovakian T-72M1 tank.




The degradation of the propellant charges stowed out in the open atop the carousel cover is reduced by the inclusion of a protective sleeve that fits over the exposed combustible charge. The sleeves are meant to protect the combustible charge from environmental damage, mostly from moisture.




Eight shells can be stowed on the engine compartment bulkhead, on top of the conformal fuel tank behind the autoloader carousel. The shells are secured to the wall using clips, which are able to accommodate any type of ammunition.


All of the stowage spaces on the engine compartment bulkhead and on the side hull wall are visible in the screenshot below (T-72B type tank hull on display).





The screenshot above gives us a good view of the ammunition from the driver's perspective, so while it may appear that a shell penetrating the hull armour would seriously jeopardize the ammo, this is not the case. Due to the highly cluttered fighting compartment and the very large distance from the upper glacis armour to the ammunition mounted to the wall (more than two meters), the ammunition has a very good chance of avoiding any damage whatsoever. The photo below, for example, shows that the engine compartment bulkhead is completely obscured behind the stabilizer components underneath the cannon and behind the seats for the commander and gunner.




All in all, there can be up to 22 additional cartridges stowed outside the carousel for a total of 44 rounds of ammunition. However, in practice, crews tend to ignore certain spaces such as the shell stowage rack on top of the carousel cover (as seen above), and some crews may decide not to have any ammunition in loose stowage at all, so the actual sum total of loosely stowed ammunition can be anywhere from 22 to none. Nevertheless, from a design standpoint, the fact that the T-72 has a total ammunition capacity of 44 rounds when the T-54/55 had only 43 and the T-62 had just 40 - while having smaller cannons and slightly larger silhouettes - is a highly noteworthy achievement and a grand step forward in design efficiency.

However, ammunition carried in loose stowage can be a huge liability in battle, as is has been proven to be the main cause of irrecoverable or catastrophic tank losses. The loose ammunition stowed in the hull is still somewhat secure, but the ammunition in the turret constitutes a significant risk to the survival of the crew. As the diagram below shows (diagram taken from Tank-Net), only 2% of shots land at a height of one meter from the ground. This is good news for the carousel autoloader, but the diagram shows that 65% of shots hit the turret. As such, the benefits of the low placement of the carousel may be completely undone by loose ammunition in the turret. 






However, it should be understood that the distribution of hits fluctuates over the years. In the Second World War, the majority of hits sustained by tanks were on the hull. It is commonly thought that this was because the hulls of the tanks of the era tended to be much larger than their turrets. Later on, combat in Korea and in the Middle East showed that more hits were being taken on the turret than on the hull, creating a more even distribution between the turret and hull. Later on, it was observed by Dr. Manfred Held that in Kuwait during Operation Desert Storm (ODS), the vast majority of shots landed on the turret. The diagram below, taken from "The Main Battle Tank of Russia: Frank Conversation About The Problem of Tank Building", shows the distribution of hits in the vertical plane by percentage for the 1967 Six-day war, the 1983 Yom Kippur war and ODS in 1991.




The three black bars in the diagram indicate (from top to bottom) the bottom of the turret, the belly of the tank, and ground level. The bottom of the turret - the turret ring - is considered to be 1.5 meters from ground level, and the belly of the tank is considered to be around 0.5 meters from ground level. The hull is therefore considered to be around 1 meter tall.

As you can see, even though the distribution of hits was not very consistent across the three conflicts, the fact that the lower half of the hull (between 0.5 to 1.0 meters) statistically sustained the fewest hits was universally true for all cases. The turret ring sustained the greatest number of hits statistically, which makes sense as the turret ring would be the center mass of any tank in the sights of an enemy gunner.



The total time needed to restock the tank with its entire complement of ammunition takes between 15 minutes to 20 minutes. Most of that time is taken up by replacing ammunition in loose stowage, since there are multiple nooks and crannies that can only be accessed by turning the turret to a specific direction. For that reason alone, it should also take more than the usual 4-5 minutes to reload the carousel using the ammunition from loose stowage.

Like the gunner, the commander has a full set of autoloader controls at his disposal, and he is responsible for placing the ammunition into the carousel during the reloading procedure, so a special control box for operating the autoloader reloading system is installed at his station. In combat, the commander can either aid the gunner in selecting the appropriate shells for the target type (which he identified), or load shells for his own use in the case of the T-72B3.


If the autoloader elevator malfunctions, it is still possible to operate the elevator mechanism manually using a crank wheel (pictured). The commander and the gunner must take turns to load the cannon depending on the location of the ammunition in loose stowage. The commander would obviously load the cannon using ammunition close to him, and vice versa. Some of the ammunition requires the turret to be oriented in a specific direction to access. The T-72A manual has a full table detailing the locations of the ammunition, the orientation of the turret needed to access it, and whose responsibility it is to load that ammunition. The benchmark time needed for a complete manual loading cycle is 26 to 30 seconds.





If the carousel fails, it is possible to manually crank the carousel and access the ammunition inside using a cranking lever located underneath the commander's seat. However, the commander would have no idea where the desired ammunition type is located in the carousel, so it is more feasible to simply use the ammunition in loose stowage.

Manual loading is something to be done in emergencies only, not only because it is much slower than normal automated loading, but because it also forces one of the two crew members to abandon his usual duties. In reality, autoloader failures are exceedingly rare (but not non-existent), so there is little need to worry about manual loading. The propensity for autoloaders to malfunction either from wear and tear or from a knock on the turret is greatly exaggerated by a few vocal armchair generals on the internet.


Loose ammunition stowage is the leading cause of total tank losses involving ammunition detonation. While the carousel is decently protected from overhead fragments, the shells and propellant charges located behind it and behind the commander's seat are not. The easiest course of action is, of course, to simply remove these loose shells before entering battle. Russian tank crews learned this and reportedly practiced this widely during Chechen campaign.





AMMUNITION






There are 4 main types of ammunition for the 125mm gun. There is no predetermined mix of ammunition. A typical loadout for a breakthrough assault or troop support mission would see that HE-Frag shells are loaded in large quantities, for example, while more HEAT and APFSDS shells would be loaded for ambushes where light vehicles and other MBTs are expected.


PROPELLANT CHARGES

 


125mm ammunition for the D-81 gun series is two-piece - propellant and projectile. Each propellant charge is contained within a thin TNT-impregnated pyroxylin-cellulose outer shell that is consumed upon firing, and the entire assembly is embedded into a steel casing stub shaped like a cup, much like a shotgun shell.

The steel casing stub is the only part of the cartridge assembly left intact after firing. In the T-64 and T-80 series, this stub is returned to the autoloader mechanism by a lever arm, but in the T-72, this stub is ejected from the tank via a small hatch at the rear of the turret roof. The diameter of the stub is 138mm, and the diameter of the rim is 150mm.




The GUV-7 electric/percussion primer is used in all of the three propellant charges designed for the D-81, giving the option to either fire the shell normally using the fire controls on the gunner's hand grips or the button on the manual traverse flywheel, or to use the manual lever-operated striker pin incorporated into the gun's breechblock.



All of the three charges have a length of 408mm.

4Zh40




Original propellant charge designed for the D-81, used since the T-64A. It uses the 15/1TR VA propellant compound. This propellant charge is rather smokey.

Mass of Complete Assembly: 10 kg
Propellant Charge mass: 5.66 kg



4Zh52





Newer propellant charge modified to produce minimal smoke upon firing without changing its ballistic potential to maintain compatibility with all shell types excluding high-energy APFSDS ones. It uses 12/7 VA propellant compound. 4Zh52 is completely interchangeable with 4Zh40.

This model has completely replaced the Zh40 in frontline use. Here is a video of the Zh52 propellant charge being opened up: click. Nowadays, HE-Frag and HEAT rounds are fired exclusively with Zh52.

Mass of Complete Assembly: 10 kg
Propellant Charge mass: 5.786 kg


4Zh63




High-energy propellant to launch APFSDS shells at even higher velocities. It uses 16/1TR VA propellant compound. It is used with newer APFSDS shells, but it seems that there is nothing to stop it from being used with older models.


Mass of Complete Assembly: 10 kg
Propellant Charge mass: 5.3kg


Fuses



V-15

Two part superquick, distance armed piezoelectric fuse. Point-detonating design that has provisions for graze initiation to allow detonation despite steep angles of incidence. It is distance-armed by inertia at a distance of 2.5 meters from the muzzle.



V-429E


The V-429E fuze is point-detonating, distance armed and with variable sensitivity settings. It has two settings - superquick and delayed. The superquick setting detonates the shell with a 0.027 second delay and the delayed setting detonates the shell at 0.063 seconds. Superquick action guarantees reliable detonation in snowy or swampy ground, and delayed action gives a small time allowance for the shell to penetrate its target before detonating. The shell is set to the Fragmentation mode when the fuze is set to the "O" position. HE mode is set when the fuze is set to the "O" position but the safety cap is left on. Delayed HE or "bunker busting" mode is set when the fuze is set to the  "З" (a Cyrillic "Z") position, and the safety cap is left on. The additional delay enables the shell to penetrate more deeply into hardened targets.

The fuze is armed by inertia; the shell experiences a momentary braking effect from the unfolding of the stabilizer fins 5 to 20 meters from the muzzle, and this is used to arm the fuze.


V-429V


The V-429V fuze is an updated version of the V-429E fuze. The safety cap has been replaced with a safety pin with a protruding ribbon. To deactivate the safety "cap", the ribbon is pulled to tug the pin out. This is much faster than unscrewing the old safety cap.





HE-Frag


The T-72 normally carries 12 HE-Frag shells in the autoloader, although this will almost certainly vary by situation. These shells have traditionally been predominant in Soviet armoured tactics, where tanks were regarded as the tip of the spear during breakthroughs. Bunkers, ATGM teams and troop concentrations - not tanks - were the bane of any and all armoured targets, and thus became high priority targets. Heavy breakthrough tanks with thick armour for charging down anti-tank guns to clear the way for calvary tanks were once the main counterforce, but with the advent of the Main Battle Tank and the phasing out of heavy tanks, the T-72 takes over this role in full, fulfilling both the role of a breakthrough heavy tank and calvary tank. HE-Frag shells therefore comprise the most important part of the T-72's loadout.





The V-429E fuse gives 125mm HE-Frag shells a great deal of flexibility. When attacking infantry in the open or in covered positions, such as anti-tank teams, advancing troops, or machine gun nests, the fuze should be set in the "superquick" mode, giving it a delay of 0.027 seconds to ensure that the shell will detonate instantly upon meeting soft ground like mud and snow, allowing it to exploit its thick steel shell to its fullest as shrapnel.

When attacking reinforced concrete targets like bunkers and pill boxes, the shell should be set in the "penetrating" mode, giving it a delay of 0.063 seconds, allowing the shell with its thick steel casing to travel a fair distance into target material before detonating. This is great for bunker busting because the impact of the big, heavy shell creates fractures, cracks and fault lines in concrete, making it a lot easier for the explosive charge to shatter and blow apart the entire structure. If targeting non-hardened buildings like houses, the shell could pass through cinder block or brick walls and explode on the other side of the wall.

With that in mind, HE-Frag may even be used as a substitute to more specialized anti-armour shells like APFSDS and HEAT against heavy armour under certain circumstances, like when all other ammunition has run out, or if effective destruction cannot be achieved. A direct hit will likely result in the debilitating disability of the cannon, destruction of aiming devices and the destruction of the driver's vision blocks, producing a firepower and mobility kill. In many cases, the driver of a modern tank has an unsettlingly high probability of being killed or at least severely injured by a hit to the turret or glacis due to insufficient blast attenuation. The explosion of a large caliber HE round on the turret ring will most certainly send spall and fragments shooting down into the driver's neck through the thin hull roof. The T-72 itself is vulnerable to this, as the roof over the driver's head is a mere 20 millimeters of steel, but conversely, the T-72 is very capable of inflicting the same damage on most legacy NATO tanks, which often do not have spall liners. This makes it exceptionally easy for a 125mm HE-Frag shell to kill, maim, and injure the crew behind the armour of all-steel tanks like the M60, Chieftain, Leopard 1, AMX 30, and so on. However, modern tanks sporting composite armour arrays and spall liners may not have the same vulnerability.


When set in the HE mode, 125mm shells are extremely deadly to lightly armoured vehicles. There are a few good reads available on the internet on this topic, but Peter Samsonov's translation of a report on the effects of 76mm HE-Frag shells at tanks with a variable fuse is especially enlightening. Here is a fascinating paragraph from that report:

"When firing 85 mm HE shells from mod. 1931 guns consider that they can penetrate 45 mm of armour at 30 degrees from 500 meters, and 50 mm of armour under the same conditions can be penetrated from 300 meters or closer."

If 85mm HE shells are capable of defeating 45mm of armour plate angled at 30 degrees at 500 meters, imagine what a 125mm HE shell could do?


When adjusted to the HE setting, the shell is able to punch huge holes in relatively thick armour and explode inside. The 38mm layer of steel appliqué armour on an M2A2/A3 Bradley will be entirely insufficient to stop such a shell even at long distances, and many legacy NATO tanks may be threatened across the flanks as well. The Chieftain's thin side skirts may offer too little resistance to set off the V-429E fuse, with the result being total destruction as the tank's thin (1.5-inch) side hull armour is easily perforated. The Leopard 1's thin side armour is extremely vulnerable to this shell as well. With hull side armour measuring only 30mm thick and turret sides measuring 40mm (angled at 30 degrees), even the aforementioned 85mm HE shell may potentially defeat the Leopard 1 from 500 meters. The addition of a 30mm spaced appliqué plate on the turret in later Leopard 1 variants might still not be enough to defend it from a 125mm HE shell, and even if the shell was successfully stopped, the explosion might still be powerful enough to split open the base armour plate.


Even though the T-72 carries more HE-Frag shells than anti-armour shells, you can see that this is not always a problem as HE-Frag shells have a very substantial multi-role capability. The use of V-429E fuses introduces a new field of possibilities for 125mm HE-Frag.


HE-Frag shells are quite barrel-friendly. They have an EFC rating of 1, meaning that if a barrel was rated for 1000 EFC, it would be able to fire 1000 HE-Frag shells before needing replacement.




3OF-19


Regular shell with copper driving bands. The shell has the shape of an ogive. It is interesting to note that this shell has a length of 675mm, making it the longest projectile among the three ammunition types carried by the T-72. This only changed with the inclusion of guided missiles in the T-72B, and high elongation long rod projectiles later on.


Complete Shell Mass: 23 kg
Complete Shell Length: 675mm
Wingspan (deployed): 356mm
Muzzle velocity: 850 m/s

Explosive mass: 3.148 kg
Explosive composition: TNT


It's worth noting that TNT is a relatively sensitive explosive compound. The risk of an ammo detonation is significantly higher if these shells are present.


3OF-26



Improved HE-Frag shell with compressed explosive charge of a different composition designed to provide added incendiary effect. Explosive compression means that the explosive charge has increased in density - that is, it has a greater mass for the same volume.

This shell uses plastic driving bands instead of copper ones, in an effort to reduce barrel wear.



Maximum Chamber Pressure: 3432 bar

Total Length: 676mm
Total Shell Mass: 23.3 kg
Muzzle velocity: 850 m/s

Explosive mass: 3.4kg
Explosive composition: A-IX-2 (Phlegmatized RDX + Aluminium filings) (Aluminium is pyrophoric. Detonation produces incendiary effects, increasing the chance of igniting or burning objects in its proximity)

A-IX-2 is much less sensitive than TNT. The risk of ammo detonation is much lower if these shells are stowed.




Practice HE-Frag



Practice HE-Frag shell that emulates the ballistic characteristics of live HE-Frag shells. Contains a 200-gram TNT charge to produce a bright flash that acts as a visual hit marker for the trainee gunner.


Maximum Chamber Pressure: 3432 bar

Total Length: 676mm

Total Shell Mass: 23.3 kg
Muzzle velocity: 850 m/s




HEAT-MP



The T-72 carries a substantial number of HEAT shells in stowage for its proven flexibility, high performance and economy. They are powerful enough to pierce contemporary armour in most cases and their explosive factor allows them to be used against light or unarmoured vehicles with a much better result than with APFSDS shells. HEAT shells may also be used against hardened concrete bunkers or simple earthen fortifications with good results, and it is entirely feasible to engage personnel owing to the very thick steel case containing the charge which is able to produce high-velocity splinters magnificently.


Against thickly armoured targets, HEAT shells produce deep but small holes. The secondary methods of destruction aside from the cumulative jet itself (which is the primary one) is the blast of the explosion of expanding gasses rushing through the hole in the armour, the flash of heat (capable of causing flash burns) and the spray of high velocity fragments of armour and shaped charge material following perforation, which can set internal equipment alight and injure the crew. It is difficult killing crew members without a direct hit by the cumulative jet unless there is a very significant armour overmatch, forcing HEAT shells to rely mostly on causing internal fires. But still, due to the enclosed nature of tanks, there is a high likelihood of striking at least one crew member if one could score a hit on the occupied sections of the tank.


HEAT shells also retain a characteristic advantage over APFSDS shells in that they wear down the barrel at a greatly reduced rate. One HEAT shell is only equivalent to one EFC, whereas an APFSDS shell can be equivalent to 3, 5 or even 7 EFC. This makes them the preferred choice of training ammunition during live fire exercises, besides HE-Frag shells. Training with APFSDS is not held quite as often, as scoring a hit with hypervelocity shells is obviously not quite as challenging as doing the same with shells that are travelling at almost half the speed. HEAT ammunition is also more expendable than APFSDS ammunition during live fire exercises, as it is now almost entirely useless against modern tank armour.


Vasily Fofanov's old website popularized the thinking that Soviet HEAT ammunition was more accurate than their APFSDS ammunition. One paragraph in particular has been frequently quoted:

"HEAT-FS rounds were also substantially more accurate than APFSDS (which might also be surprising to a Western reader). This is reflected in the Soviet deviation criterion, which was more strict for HEAT rounds (0.21 mil) than for APFSDS rounds (0.25 mil). However, in practice HEAT-FS rounds were even more accurate. As control trials of a random mass-production T-64A held in the 70s (the details of which were made available to the author) indicated, while APFSDS rounds hugged the outer bounds of acceptance criterion, HEAT-FS rounds actually demonstrated the average deviation of well under 0.1 mil!"

This may or may not be true, since Fofanov has admitted that the information presented in his website is mostly outdated and unreliable. Thankfully, there are more solid sources for our perusal. According to firing tables for 3BK-14M provided by Stefan Kotsch, the HEAT shell has a horizontal deviation of 0.19 m and a vertical deviation of 0.19 m. On the other hand, the firing tables for 3BM-15 - also provided by Stefan Kotsch - show that the APFSDS shell has a horizontal dispersion of 0.20 m and a vertical dispersion of 0.20 m. The gap in probable deviations remains minor even at 2 km. At that distance, 3BK-14M has a horizontal dispersion of 0.38 m and a vertical dispersion of 0.39 m, whereas 3BM-15 has a horizontal dispersion of 0.4 m and a vertical dispersion of 0.4 m. Evidently, there is some truth to the claim that Soviet HEAT ammunition was more accurate, but the enormity of the gap between the two types has clearly been highly exaggerated. Furthermore, these firing tables only represent the mechanical accuracy of the projectile and the cannon it is fired from, and does not represent the accuracy of the entire weapon system, including the aiming and gun laying devices.

In practical real world conditions, the expected hit probability of HEAT ammunition is vastly lower than that of APFSDS ammunition for a variety of factors. The most major factor is the interference of crosswinds and head or tail winds, and another factor to consider is ranging errors, particularly at longer distances. The high velocity of APFSDS ammunition (3BM-15 has twice the muzzle velocity of 3BK-14M) also makes it much easier to score hits on moving targets at any distance.



Glossary:

Wave Shaper: Object or device that infleunces the propagation of blast waves in a way that is beneficial to jet formation. Typically composed of an inert material with low sound speed.

A-1X-1: Phlegmatized RDX, consisting of 96% RDX and 4% wax.

OKFOL: Explosive compound composed of 75% HMX and 25% RDX.

Standoff Probe: Extended structure to increase the distance between the shaped charge cone and the target material, i.e, standoff.

Explosive Pressing: The process of increasing the density of explosive compounds by high-pressure mould pressing. The result is more explosive mass per volume, translating to more energy.


All of the information presented below are backed by either photographic or videographic evidence, or official documentation.


3VBK-7

3BK-12, 3BK-12M





First 125mm HEAT shell, originally for complementing the T-64. By the time the T-72 emerged, it had been long replaced by the 3BK-14. The 3BK-12 is the low cost version with a steel shaped charge liner, and the 3BK-12M is the more expensive version with a copper liner. The shell is characterized by the rather thin walls of the standoff probe, straight standoff probe, and a house shaped wave liner, as seen in the diagram above.


Projectile weight: 19.8 kg
Total Projectile Length: 678mm

Muzzle velocity: 905 m/s

Explosive Charge: A-1X-1
Explosive Charge Weight: 1760g

Shaped Charge Cone material: Steel
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle: 36°


Penetration (at all distances):
420mm RHA (unknown target obliquity)



3VBK-10

3BK-14, 3BK-14M





Updated HEAT shell with similar dimensions as the 3BK-12, but with minor internal differences. It is characterized by distinct knurls around the top edge of the main body surrounding the standoff post, probably to enable the shell to fuse even on extremely high obliquity impacts by tilting the tip towards the armour plate on a glancing blow. This shell uses a cylindrical wave shaper with a slight taper, and the standoff probe now has a slight taper.

The BK-14M warhead uses a copper liner ("M" stands for "med", which means "copper" in Russian). This results in improved penetration performance, but at slightly higher cost. The wave shaper is different.


Maximum Chamber Pressure: 2900 bar

Projectile Weight: 19.8 kg
Total Projectile Length: 678mm

Muzzle velocity: 905 m/s

Explosive Charge: OKFOL
Explosive Charge Weight: 1760g

Shaped Charge Cone material: Steel
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle: 36°
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)


Standoff probe diameter: 65mm tapering to 45mm
Standoff probe wall thickness: 7.5mm

Penetration (3BK-14):
450mm RHA at 0°

Penetration (3BK-14M):
480mm RHA at 0°



3VBK-16

BK-18





The 3BK-18 is a further improved design. Visually identical to previous designs, but differs in that it features an aluminium shaped charge cone. Aluminium is pyrophoric, meaning that it burns when finely pulverized and when under extreme stress. Under those conditions, it can produce a very fierce incendiary effect, increasing its killing power in the event of a perforating hit. The noxious fumes produced by burning aluminium may also force the crew to leave their vehicle.

Unlike the lightly tapered wave shaper of the 3BK-14, it has a cylindrical one, which coincides with the usage of a different cone material with different physical properties. Like its predecessors, it has distinct knurls around the top edge of the main body.

The 3BK-18M is a variant of the 3BK-18 using a copper cone. Both models are very widespread in current Russian Army stocks.

The 3BK-18 is characterized by its thickened walls, both for the warhead casing and for the standoff probe. This presumably translates to a significant improvement in the anti-personnel capabilities of the shell compared to earlier designs, and the more robust standoff probe may be beneficial for other reasons.





Maximum Chamber Pressure: 2900 bar

Total Length: 678mm
Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s

Explosive Charge: OKFOL
Explosive Charge Weight: 1760 g

Shaped Charge Cone material: Aluminium
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle: 36°
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)

Standoff probe diameter: 65mm tapering to 45mm
Standoff probe wall thickness: 7.5mm

Penetration (3BK-18):
500mm RHA at 0°

Penetration (3BK-18M):
550mm at 0°


3VBK-17

BK-21



Improved shell featuring a dirty copper-coloured cone with extreme elongation. It uses a cylindrical wave shaper. It isn't seen very often.


Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s

Explosive Charge: OKFOL
Explosive Charge Weight: ~1400g (?)

Shaped Charge Cone material: Copper or Brass
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle: 36°
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)

Penetration:
~650mm at 0°


BK-21B


Radically improved, using a DU-Ni alloy cone. DU-Ni cumulative jets exhibit superior jet consistency and will not break up in flight as quickly as other materials, offering very good overall performance. The new liner also seems to offer superior penetration against complex armour arrays. Unfortunately (or fortunately, depending on your perspective), production costs and the difficulty of controlling the variables associated with using it makes usage impractical. The shell uses an arrow-shaped wave shaper.

DU as a material for shaped charges is highly polluting. If perforation occurs, the interior of the tank will be filled with highly dangerous DU particles, which will be very difficult to remove. Whereupon the lack of perforation, the hole created in the armour array will still contain DU particles, posing a hazard for crew and technicians working in and out of the target object or vehicle.

DU is also pyrophoric, and like aluminium, will wreck havoc in the confined spaces of an armoured vehicle. 


Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s

Explosive Charge: OKFOL
Explosive Charge Mass: ~1400g (?)

Shaped Charge Cone material: DU-Ni
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle type: Medium, 60°
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)

Penetration: >650mm


3VBK-21

BK-25



A HEAT shell that is very seldom seen. Cutaway photos show that it has a silvery-gray shaped charge cone, but its shape and dimensions betray that it is definitely not steel nor aluminium like the ones before it. It is very likely that it is tantalum, which is known to be a viable cone material. It uses a rather oddly rounded wave shaper. Very little is known about this shell other than these facts.


Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s

Explosive Charge: OKFOL
Explosive Charge Mass: ~1400g (?)

Shaped Charge Cone material: Tantalum / Tantalum alloy
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle type: Medium, 60°
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)

Penetration: ~600mm (?)


BK-25


Same interior configuration as its parent but with a bulkier bevel connecting the standoff post to the main body. Liner material is unknown, but all other components appear to be identical.


Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s

Explosive Charge: OKFOL
Explosive Charge Mass: ~1400g (?)

Shaped Charge Cone material: (?)
Shaped Charge Cone diameter: 105mm
Shaped Charge Cone angle:
Shell wall thickness: Tapering from 7mm (front) to 17.5mm (base)

Penetration: ~600mm (?)


3VBK-25

BK-29





Relatively recent (late 80's) shell with tandem warhead configuration primarily to aid in penetration of complex armour arrays and to defeat ERA-equipped targets. Despite being heavier than its single-charge predecessors, it somehow travels slightly faster.

The precurser shaped charge is located halfway down the standoff probe and may be rightfully considered a fully-fledged warhead all on its own, having a considerable explosive charge and complete with its own standoff accounted for. The use of a precursor warhead makes it very effective against the special armour of NATO tanks from the early 80's, prior to the use of depleted uranium in the armour of the Abrams tank.

This shell is characterized by the lack of "teeth" on the front edges of the primary warhead case, and the new fuse, which is fully conical in shape. The shell uses a hemispherical wave shaper. Both charges have base fuzes.

The 3BK-29M is same shell as its parent, but with a copper liner. Whether both the precursor and the main charge use copper is unclear, but it is likely.



Projectile Weight: >20 kg
Muzzle velocity: 915 m/s

Explosive Charge: A-1X-1
Explosive Charge Weight: (?)


Precurser Explosive Charge: A-1X-1
Precurser Charge Cone material: (?)
Precurser Charge Cone diameter: 40mm


Primary charge penetration (without precurser/after reactive armour): ~620mm at 0°
Primary charge penetration (after precurser/without reactive armour): ~820mm at 0°



BK-29 should be considered the most important development in tank cannon-fired HEAT ammunition in recent times, as it is the only example of a tandem warhead HEAT tank shell in service. Now that we know of the armour composition of the M1 Abrams, we can speculate on how BK-29 would fare against it. One of the things that we can be certain about is that the front armour plate protecting the NERA array is relatively thin. The precursor charge of BK-29 could probably punch through the armour plate, enter and leave holes in several of the NERA plates and leave an open channel through which the main warhead can then pass through and defeat the main armour, since the precursor and the main charge are coaxial. With the extra spacing created by the large and mostly hollow armour array, the main charge could easily reach its optimum standoff distance and reach its maximum penetration power. Following this train of thought, it is probable that BK-29 can defeat the front hull armour of the M1A1 Abrams, but probably not the turret, since the thickness of the new turret composite armour was substantially increased over the M1.

However, it will not be able to defeat the turret cheeks of a T-72B. The Kontakt-1 boxes that encapsulate the composite armour of the T-72B will reduce the effect of the precursor charge of BK-29 (and indeed, any tandem warhead projectile) so much that it will be easily stopped by the relatively thick front wall of the armour cavity in the turret, meaning that the primary warhead will still have to deal with the untouched NERA armour contained within, and the warhead will most probably fail to defeat the entire array.



3VBK-27

BK-31


Enigmatic and ingeniously designed triple-charge HEAT shell. It is probably not in service at present. It can penetrate 800mm of steel armour with a hardness of probably about 280 BHN, as demonstrated by a cutaway.


Total length: 665mm

Penetration: 800mm RHA (No reactive armour)


From Vasily Fofanov's website


Practice rounds


VP5



Single-charge inert HEAT warhead designed to exactly emulate the ballistic trajectories of the 3BK-14 and 3BK-18 shells. There is a 200-gram squib inside the warhead that acts as a visual hit marker for the trainee gunner.

Total Length: 678mm
Projectile Weight: 19.8 kg
Muzzle velocity: 905 m/s



BK-29I



Training round imitating the exact flight characteristics of the 3BK-29 shell.




APFSDS



Despite pioneering APFSDS shells with the introduction of the 2A20 115mm gun, the Soviets never had the technology to mass produce true long rod tungsten or depleted uranium projectiles until the mid-80's, whereas the Americans had already fielded the M774 DU APFSDS round since the mid-70s. So they were in a bit of a quandary. Their best APFSDS rounds were technologically crude sheathed core projectiles that were incredibly economical (very little tungsten is present in them), but limited in scope and growth potential.

According to a firing table provided by Stefan Kotsch, 3BM-15 suffers a 138 m/s drop in velocity over 1 km from the muzzle, and a 127 m/s drop from 1 km to 2 km. This is slightly greater than the drop suffered from the 115mm 3BM-3 shell. The ballistic characteristics of 3BM-15 can be used as a surrogate for every other APFSDS shells from the 3BM-9 to the 3BM-22, as they all share the same torpedo shape. Compared to Western APFSDS, Soviet shells suffers from very high drag - more than twice as high.


The only way to improve their performance without any radical design changes was to increase mass and increase speed, but this could not be easily done with the 115mm gun. The HEAT rounds for the "Molot" were good, but undependable due to terrible accuracy, so they weren't of much use even though they were more than capable of taking out any tank, bunker or anything in between. For the moment, the "Molot" was more than capable of killing any NATO tank at average combat distances, but it would not have been enough had there been even a modest uparmouring like the Stillbrew modification on the Chieftain. They never really got past this problem until the 80's when the Soviet ammunition industry progressed sufficiently to begin the mass production of long rod penetrators, but before that, in one form or another, all 125mm APFSDS ammunition followed the basic principle as the 3BM-3 introduced in 1961. The use of steel caps meant that the performance of these early APFSDS shells at high obliquities was somewhat lower than at lower obliquities, whereas it was the exact opposite with new, long rod monobloc rounds like the M111 "Hetz". Incremental improvements reduced the severity of the issue over time, but the problem was only truly solved when long rod tungsten alloy or depleted uranium shells were introduced in significant quantities in the mid 80's.

Producing high-quality weapons-grade tungsten carbide and other tungsten alloys in slug form was difficult and expensive, and extruding tungsten alloy rods was no mean feat. The equipment simply didn't exist in the USSR.

The main defeat mechanism of APFSDS shells against armoured targets is by killing crew members with shards and fragmentation of the shell after armour perforation, but a secondary mechanism is setting internal equipment alight, just like HEAT shells. The huge kinetic energy and extreme forces imparted during armour defeat results in some of that kinetic energy being converted to heat energy, which results in a flash of heat and a shower of high velocity sparks from particles of both armour material as well as penetrator material. And of course, the flash and sparks work to set flammable items on fire.


The selection of APFSDS ammunition available to the T-72 gave it the upper hand in any engagement with any one of NATO's heaviest, until the new generation of tanks rolled out in the early 80's. The heaviest NATO tank before the Leopard 2 and M1 Abrams was, of course, the Chieftain, but we already know how it would fare against the APFSDS rounds fired from the T-72. The Chieftain Mk.10, on the other hand, is worth more scrutiny.

In 1986, the Chieftain Mk.10 was introduced and Stillbrew armour made its debut. It is rather difficult to find a credible source that describes Stillbrew with any amount of useful detail, but Volketten has done some research into the topic and claimed in an article published on Rita Sobral's blog that Stillbrew was a form of composite armour that worked like NERA.




The thickness of the frontal projections of the turret are well known; an average of 125mm at 60 degrees across the cheeks on both sides, and 158mm at 45 degrees at the base. However, there is some difficulty in determining the exact thicknesses of Stillbrew over the various curves and bumps of the turret. Volketten states that the center part of the Stillbrew plate over each cheek had a thickness of 167mm, equivalent to a 150mm rolled armour plate, and these photos from the Leicester Modellers website help us estimate the thickness of the add-on cast steel plates to be exactly 60mm thick over the right mantlet (no rubber) and less than 100 for the edge of the plates over the cheeks.




U.S Patent 4848211 is the patent for Stillbrew. If any doubts persist, note that one of the inventors listed is a "John H.T Brewer", and that the priority date for the patent is 4 June 1986. The patent states that the armour is a composite armour, but makes absolutely no mention of the movement of the add-on plate, and it is easy to see why. The add-on cast armour plate is simply too thick and too heavy to move with the limited amount of energy transferred to the rubber interlayer, and the plate is securely screwed to the turret by large countersunk stainless steel screws. The countersunk screws is the most significant piece of evidence, because the beveled rim of the screws (something like this) pins the plate down and prevents the plate from sliding up the shaft of the screw.

One of the confirmed roles of the rubber interlayer is to absorb the shockwave of an impact landing on the add-on cast front plate, and to prevent the plate from falling off in much the same way as the rubber mounting blocks found on the Leopard 1A1A1. The function of the rubber is almost certainly as a simple sandwich material in the same way silica was used in siliceous core armour and GRP was used in the sandwich armour in the upper glacis of the T-64A and the T-72. The 50mm interlayer has an effective thickness of 100mm when sloped at the 60 degree angle of the turret, so the effects of the rubber layer are considerable, especially against shaped charge jets.

Adding up the layers, we find that the total thickness of the armour has now increased to more than 500mm. This would have made the turret immune to all Soviet 125mm HEAT shells as well as any APFSDS round from before 1985, probably down to point blank range. Interestingly, Stillbrew appears to give Chieftain more armour than the M1 Abrams possessed, if the oft-quoted figure of 400mm vs KE is believed. Stillbrew can be considered a good and cheap method of increasing the protection of the Chieftain up to the level of NATO's new generation tanks, but it must be emphasized that this was achieved by simply adding more steel on top of steel, not by some ingenious new type of armour.


Having said this, it must still be understood that Soviet 125mm APFSDS ammunition never had any real trouble defeating NATO tank armour from the same era. Stillbrew, for example, was introduced in 1986, but by 1985, the "Vant" depleted uranium monobloc shell with more than 500mm of penetration at 2 kilometers became available in the Soviet arsenal. This would have handily defeated the Chieftain Mk. 10. Even non-NATO tanks like the Strv 103 from 1967 would have fared very poorly against Soviet 125mm guns. Ointres.com reports that during a Swedish test in the early 90's involving an Strv 103 and a T-72M1 purchased from the ex-GDR, 3BM-22 shells fired at the frontal armour of the S-tank proved to be so powerful that it went through the front and came out the back, albeit at an unknown distance. It is not difficult to imagine that the 3BM-15 shell from which the BM-22 was derived would produce a similar result at a slightly closer range, and combat experience with the T-62 and its 115mm APFSDS ammunition had shown that it was more than enough against Iranian Chieftains. This changed with the introduction of the new generation of NATO tanks, but even then, the sides of the hull and turret remained inconveniently soft, so Western engineers had to find creative solutions.


The Leopard 2 shielded the crew compartment from the side with three heavy 100mm steel plate modules (consisting of two 50mm plates each) bolted to the side of the hull just over the first two roadwheels (Source). From an incidence angle of 30 degrees from the longitudinal axis of the tank, this arrangement yielded a 200mm thick sloped plate. Absolutely miserable protection against long rod penetrators and HEAT warheads, but quite effective against the sheathed core APFSDS rounds common in the Red Army inventories. Refering to this report here (link), it's clear what they were going for. The 125mm APFSDS rounds that are so effective against individual homogeneous plates also shatter magnificently after passing through them. This would have been incredibly lethal to the older plain-steel legacy tanks like the M60 and Leopard 1, but the 100mm ballistic plates on the Leopard 2 would be capable of stripping the steel from cored projectiles like 3BM-15 and 3BM-22, leaving only the small tungsten carbide core to travel on by itself. Though lethal enough on its own, the small size of the tungsten carbide core and the limited fragmentation spread produced by passing through the 50mm base armour of the side hull is too limited to be of much worry. The probability of achieving a first round kill was thus greatly reduced. The Abrams implemented a similar design with its 60mm composite sideskirts. These were thinner than the Leopard 2's 100mm plates, and the Abrams' base armour is much thinner at only 28.575mm (1 1/8 inches 420 BHN welded hard steel bilayer), but they covered the hull all the way down to the fifth roadwheel. Such a configuration should be sufficient against Soviet APFSDS rounds that had their tungsten carbide cores near the nose, and still somewhat effective against ones that had them near the tail. These protective measures would be useful until the introduction of Soviet monobloc long rod APFSDS rounds in the mid-80's, which, incidentally, is not far from the introduction dates of the Leopard 2 and Abrams.


The Soviet standard for certifying armour piercing projectiles is V80, meaning that the expected consistency of achieving full armour perforation given a certain projectile velocity must be 80%. In formulas, V80 must replace V50 (50% chance of armour perforation). For example, if a certain projectile has to penetrate 500mm of steel, then at least 80% of all projectiles of that type must achieve that standard. This is very different from the NATO standard of only 50%. Soviet standards were not only stricter, but the steel they used for targets was of a greater hardness than NATO targets. In reality, the given penetration data does not correspond to the actual achievable penetration of these shells.



3BM-10

3BM9






An extremely rudimentary projectile with a maraging steel penetrator body. Maraging steel is preferred for its malleability, which prevents the high-velocity shell from shattering outright upon impact, but maraging steel is superior to normal steel in that it retains its strength with its malleability. However, the softness of the steel (about 300 BHN) hampers its ability to penetrate armour somewhat. The decision to use a pure maraging steel projectile without an armour piercing cap must have been a deliberate one, as tool steel with a hardness up to 600 BHN had been used as early as 1945 in the BR-412B 100mm APBC shell. 3BM-9 might be an attempt to conserve tungsten carbide while achieving the same performance as 115mm tungsten cored rounds, as 3BM-9 can penetrate the same armount of armour as 115mm 3BM-3 tungsten core rounds but without doesn't use any tungsten carbide itself. Besides that, maraging steel is renowned for being very easy to work with and cheap, so the existence of 3BM-9 must be for economic reasons.

Nevertheless, 3BM-9 was more than enough for any NATO tank of the time, including the Chieftain. According to a Soviet analysis of an Iranian Chieftain captured by the Iraqi army during the early part of the Iran-Iraq war, available here on Andrei Tarasenko's btvt.info, the Chieftain Mk.5 had totally insufficient protection even from the 3BM-9. The frontal part of the entire turret, hull upper front plate and lower front plate could all be defeated at 3 km or more. This essentially means that the T-72 Ural can defeat NATO's toughest tank at any reasonable combat distance with zero expenditure of valuable tungsten.


3BM-9 is quite remarkable for being the first service munition that is fired at truly hypersonic speeds (Mach 5+). This shell used a steel "ring" type sabot with a copper driving band. Sabot construction is critical to shooting accuracy, and the steel "ring" type sabot was perfectly fine compared to any other APDS sabot at the time. Plus, any deficiencies in accuracy from the sabot would be unnoticeable given the gobsmacking speed of the projectile coming out of it.





This is all just speculation, but it is possible that 3BM-9 might have been what T-72 Urals were given for their first year of service as a sort of intermediary before the supply of 3BM-15 shells (introduced in the same year as the T-72 Ural) was assured. T-64s should be the first to transition to the newer ammunition, and the T-72 might have had to wait.



Muzzle velocity: 1800 m/s

Mass of Projectile: 3.6 kg
Mass of Sabot: 2.02 kg
Total Mass: 5.67 kg

Length of Projectile: 410mm
Minimum Diameter of Projectile: 36mm



Certified Penetration at 2000m:

245mm at 0°
185mm at 45°
140mm at 60°


Certified Penetration at 1000m:

300mm at 0°
160mm at 60°

(According to a Soviet GRAU document)



Penetration at 2000m:

290mm RHA at 0° (Zaloga)


The achievable armour penetration of 3BM9 is quite a bit higher than its certified penetration capability. Post armour penetration effects are very powerful, due to the large hole created by the inefficient steel penetrator.




3BM-16

3BM-15

The 3BM15 is a steel-sheathed, tungsten-cored APFSDS shell with a tri-petal steel sabot, introduced in 1972. It is externally identical to the 3BM-9 projectile.

Although decently hefty and very speedy, the shell primarily relies on a small tungsten carbide subcaliber core to do the job. A ballistic windshield was crimped onto the soft steel shock absorber cap, whose duty was to prevent ricochets and to soften the shock of the impact to the rest of the projectile body. The projectile body is maraging steel, which more or less peels away upon impact while the core continues onward - an extremely inefficient arrangement. The maraging steel body creates a crater almost as large as the one created by the 3BM-9, but not quite so large.

All this doesn't mean that it cannot go through large amounts of steel, however. The 3BM-15 is certified to penetrate 150mm RHA at 60 degrees. The photo below shows the result of the shell penetrating a 200mm steel block (of unknown hardness) at 0 degrees, entering from the top and exiting from the bottom, leaving very large holes on either end. The 3BM-15 clearly outmatched all NATO armour at the time, which could not stand up to it even in the thickest places.

The photo below shows the result of a steel block meeting a BM-15 projectile on a perpendicular impact at an unknown range. steel body disintegrated inside the armour as it entered, but the tungsten slug passed onwards leaving a very clean tunnel (indicating that it still had plenty of momentum).




In the event of a penetration whereby the steel body has not peeled off fully, it functions to blast the interior of the target tank with hundreds of large pieces of steel - absolutely devastating to interior equipment and crew members alike. Thus, while the 3BM-15 was lethal to all NATO tanks of the time, it was exceptionally lethal to tanks like the AMX-30 and Leopard 1, which had particularly thin armour. However, this shell became essentially useless against new NATO armour emerging in the early 80's, like the Leopard 2 and the M1 Abrams, as these new generation tanks had thick steel or composite sideskirts designed to expend the steel projectile. The tungsten carbide slug could not be stopped so easily, of course, but a small slug could do only a fraction of the damage that the full package would have done.

3BM-15 uses the same steel "ring" type sabot as the 3BM-9. The photo below is from a Rheinmetall brochure on PELE ammunition, demonstrating a modified 3BM-15 PELE round in flight and the airflow around the components of the round. The sabot was unmodified.



An incremental propellant charge is wrapped around the projectile body.


Mass of Incremental Charge: 4.86kg
Maximum Chamber Pressure: 4440 bar

Muzzle velocity: 1785 m/s

Steel body maximum diameter: 44mm
Steel body minimum diameter: 30mm
Armour piercing cap diameter: 20mm
Core diameter: 20mm

Length of projectile only: 435mm
Length of armour piercing cap: 20mm
Length of core: 71mm

Mass of Steel body: 3.63kg
Mass of Core: 0.270 kg

Total Mass of Projectile: 3.83 kg


Certified penetration at 2000m:

400mm at 0°
200mm at 45°
160mm at 60°

(According to a Soviet GRAU document)


The firing table for the 3BM-15 are available to the public, courtesy of Stefan Kotsch.


 


The steel "wedge" in front of the tungsten carbide slug is an armour piercing cap to protect it from shattering the instant it impacts the target, and to improve performance on highly sloped armour.

3BM-15 was designed with adherence to the same design principle as the older 115mm 3BM3 round. 3BM3 was intended to have armour penetration capabilities similar to or exceeding that of a contemporary APDS shell without incorporating as much tungsten carbide in its construction. 3BM3 was highly successful in this regard, as it managed to achieve more penetration than BM-8 APDS for the 100mm D-10T using only a tenth of the amount of tungsten carbide in its core. It achieved this mainly by being faster, because by having a long steel rod behind the tungsten carbide core and not in front of it, it was the core that impacted the armour first, and it was the core that penetrated the most armour. 3BM-15 had a better armour piercing cap design, and a slightly lighter core (0.27 kg vs 0.3 kg) but it achieves its superior penetration mainly by being faster. We can confirm this theory by simply checking the penetration values of 3BM3 against the 3BM-15 at the same velocity. We know that 3BM3 loses speed at a rate of 130 m/s per kilometer, and that the 3BM-15 must lose speed at an even faster rate since it has slightly larger (by 1 cm) diameter stabilizer fins. So assuming that 3BM-15 loses speed at a rate of 140 m/s, we can calculate that 3BM-15 will only be 20 m/s faster than 3BM3 at 1 km when it is at 2 km. So is the penetration of 3BM-15 at 2 km comparable to 3BM3 at 1 km? Absolutely. At 0 degrees, 3BM-15 penetrates 310mm at 2 km, and 3BM3 penetrates 300mm at 1 km. The difference can be explained by the better armour piercing cap and some error in the assumed rate of speed loss.

Compared to the tungsten carbide core of 3BM-8 (far left), the core for 3BM-15 (far right) is incredibly tiny, and yet 3BM-15 penetrates far more armour.






(Credit for photos to PzGr40 from wk2ammo.com)

(Sourced from unisgroup.ba, wk2ammo.com, Vasily Fofanov)



3BM-17

3BM-18


This shell is essentially identical to the 3BM15 externally, but it lacked the tungsten carbide core of its parent and only had a modified AP cap, presumably to reduce ricochet probabilities. Thus, it was slightly superior to the 3BM9, but still far behind the 3BM15 in penetration performance.



Muzzle velocity: 1780 m/s


Total length: 548mm
Length of Projectile only: 435mm


Certified Penetration at 2000m:

310mm RHA at 0°


Average penetration at 2000m:

330mm RHA at 0° 



3BM-23

3BM-22



A derivative of the 3BM-15. It began mass production in 1976, but only formally entered service in 1977. It features an enlarged and improved armour piercing cap in front of the tungsten carbide core, presumably to further improve performance on heavily sloped armour plate. The projectile is shorter than the 3BM-15, and it retains the steel ring-type sabot. The most significant difference between the 3BM-22 and the 3BM-15 is the armour piercing cap, which is placed in the same location as before, but now has a larger diameter than the core beneath it, and protrudes beyond the steel body, so that the armour piercing cap strikes the target before the rest of the projectile. This greatly improved its performance on sloped armour - its performance on a plate angled at 60 degrees is higher than on a perpendicular plate.

Despite the rather high armour penetration capability, this projectile would have been woefully inadequate against the special armour arrays found on the new NATO tanks appearing in the early 80's. This is because the composite design of the projectile is simply too fragile to handle strong lateral stresses - being made from steel and all - so the projectile is can be defeated by anything more complex than a simple solid block of steel. Even a simple double layer of spaced steel armour will work against a round like 3BM-22; the spaced plate strips the armour piercing cap in front of the tungsten carbide slug, and the naked disembodied slug travels forward and impacts the main armour with a high possibility of shattering, or even ricocheting if the obliquity of the base armour is high (due to its ogive tip). Of course, it wouldn't be enough to put two thin steel plates together and call it a day, since there is also the large and heavy steel body travelling at 1700 m/s+ to consider, but even so, the penetration capability of the projectile would still have been severely compromised. The NERA array of the M1 Abrams would be exceptionally good at defeating this round.

It has been claimed that the M1 Abrams is equivalent to 400mm of RHA steel, but it is obviously not possible for this to be true for the simple reason that composite armour is simply too complex to be distilled into a single figure in RHA equivalence.




The "400mm" figure might hold up in the context of a sheathed long rod penetrator, since those became the norm during the 80's and would undoubtedly be tested against the armour of the Abrams, but even so, the RHA equivalency rating should not be used to determine if Soviet APFSDS ammunition could or could not penetrate the armour. Having said that, it must be noted that since we know the configuration of the hull front armour of the M1, there is quite a good chance that at shorter ranges, even the damaged steel tail of the projectile might be able to punch through the back plate after passing through the NERA array.

Existing stocks are currently being expended in live-fire exercises, for which older projectiles are favoured since they are less harsh on the gun barrel.


Mass of Incremental Charge: 4.86 kg
Maximum Chamber Pressure: 4440 bar

Muzzle velocity: 1785 m/s

Steel body maximum diameter: 44mm
Steel body minimum diameter: 30mm
Armour piercing cap maximum diameter: 30mm
Armour piercing cap minimum diameter: 27mm
Core diameter: 20mm

Length of projectile only: 400mm
Length of armour piercing cap: 88mm
Length of core: 71mm

Total projectile mass: 4. 485 kg
Mass of core: 0.270kg


Certified Penetration at 2000m:

380mm at 0°
200mm at 60°




3BM-27 (Nadezhda)

3BM-26




Introduced in 1982, the 3BM-26 projectile is the most optimum Soviet APFSDS shell that is still based on the composite design principle of a small tungsten carbide slug placed in a steel long rod body. Unlike previous shells that used the steel "ring" type sabot, the 3BM-26 projectile rides on a "bucket" type sabot made from a lightweight aluminium alloy. The new design of the "bucket" type sabot interfaced with the projectile via fine threads as opposed to six large threads as found on the "ring" type sabots, and this significantly contributed to the improved accuracy of the shell, although the magnitude of the improvement is not known. This shell was the first to use the high-energy Zh63 propellant charge, giving it an extra performance boost over previous models (the incremental charge has the same composition as 4Zh63).

Unlike the 3BM-22 and 3BM-15 that preceded it, the tungsten carbide core is located at the tail of the projectile body. This means that it will only begin to come in contact with the armour only when the steel body in front has been completely expended from doing its share of the work. There is an air space forward of the core to allow it room for forward travel as the rest of the body decelerates within the target material. This is to allow the core to retain the same 1720 m/s velocity in spite of the erosion and slowing down of the steel body in front of the core.

At the very front is the ballistic windshield, crimped onto the armour piercing cap, which is now slightly larger. The increased length of the armour piercing cap did not significantly affect the performance of the 3BM-26 on oblique targets, as evidenced by the fact that the penetration of this shell for a plate at 60 degrees is the same as the 3BM-22.


Out of all Soviet slug-within-a-steel body designs, this projectile has the best prospects against the NERA armour of the M1 Abrams and Leopard 2. The projectile is still as vulnerable to fracturing and disintegration when strong lateral forces are imparted onto the steel body by the moving plates of NERA or ERA arrays, but due to the location of the tungsten carbide slug, 3BM-26 still retains its most potent component upon reaching the back plate of the armour array. In previous designs, the tungsten carbide slug could be dislocated from the rest of the projectile after emerging from behind a spaced armour plate, whereby it could yaw and shatter upon impact with the base armour, while the intact steel tail of the projectile could continue on and do the little damage it could. The use of a small tungsten carbide slug instead of a long penetrator like on the M735 is undoubtedly an anachronism, but at least it is an economical solution to the lackluster technological capabilities of the munitions industry at the time. An additional economic advantage to 3BM-26 is that it uses the same tungsten carbide core as previous APFSDS models, so it is possible to scrap old stocks of ammunition and recycle the cores to be used in a more effective carrier.


Mass of the sabot: 2.2 kg

Mass of the projectile only: 4.8kg
Mass of core: 0.270 kg

Length of projectile only: 395mm
Length of armour piercing cap: 115mm
Length of core: 71mm

Maximum diameter of the projectile: 36mm
Maximum diameter of armour-piercing cap: 36mm
Minimum diameter of armour-piercing cap: 27mm

Muzzle Velocity: 1720 m/s

Certified penetration at 2000m:

410mm at 0°
200mm at 60°


Despite total obsolescence, this shell is still used in reserve units. Their fate is to be expended in live firing exercises. High readiness units in the Western military district have gotten rid of this shell long ago.



3BM-33 (Vant)

3BM-32



Having being informed of new Western developments of advanced composite armour, GRAU set forth new requirements to defeat future dynamic armour in the mid-70's. In 1977, work began on new APFSDS projectiles to accomplish this. The new projectiles would be based on totally new design concepts in order to avoid the limitations of the previous cored design principle. The first result of the development process was "Vant".

3BM-32 "Vant" is a jacketed depleted uranium projectile introduced in 1985. It is quite short, but still longer than its predecessors. The depleted uranium-nickel-zinc alloy penetrator rod is encased in a steel jacket of an unknown alloy. The sheath was thinner over the front and rear thirds of the projectile, but it was much more pronounced in the middle. The projectile is aesthetically similar to the 120mm DM13 APFSDS shell. The "bucket" style sabot design from the 3BM-26 was carried over and modified, which meant that large bore-riding fins were still necessary. This was a problematic source of drag, resulting in the "Vant" being slower than its foreign counterparts at long range despite its higher muzzle velocity.

The DU rod is made from an alloy based on Uranium-238. The reason why the depleted uranium penetrator was so short compared to the ones commonly used today is simple; they couldn't make them longer. Nevertheless, "Vant" could still be considered a decent round for the mid-80's. The long rod penetrator is somewhat longer than the 105mm M774 and M833, but it was technologically outclassed by the American 120mm M829 which arrived a year before (1985). However, pure length was not the only criteria for success by the 1980's, because tanks with composite armour protection were becoming more and more common outside of the Soviet Union. In that context, the jacketed long rod penetrator of the "Vant" may have been on equal footing with the longer monobloc M829 penetrator against modern threats, as it is understood that jacketed heavy alloy long rod projectiles may have better performance against spaced armour and certain types of composite armour than monobloc projectiles of the same mass. 


With that in mind, it is important to note that the use of a jacket was still primarily a method to maintain the integrity of the rod during acceleration in the gun barrel and during flight, which was commonly done for early long rod heavy alloy projectiles. According to "Numerical Analysis and Modelling of Jacketed Rod Penetration", the common use of steel jackets on early long rod penetrators was due to the poor mechanical properties of the heavy metal alloys at the time. The most serious issue was the shearing of the threads that held the long rod penetrator to the sabot during acceleration inside the gun barrel when firing, which is why the steel jacket over the depleted uranium rod in "Vant" is thickest in the middle, where it joins with the sabot.

The weakness of jacketed long rod penetrators is its reduced penetration power against homogeneous steel armour, as detailed in "Numerical Analysis and Modelling of Jacketed Rod Penetration". In general, decreasing the thickness of the steel jacket relative to the diameter of the rod to a ratio of 0.1 results in the smallest degradation of penetration against steel armour, and may actually increase the residual length of the penetrator emerging from behind the armour plate, albeit at a lower velocity compared to a monoblock rod. However, reduced penetration against homogenoeus steel targets was hardly an issue by the mid-80's.


Muzzle velocity: 1700 m/s 

Mass of the projectile: 4.85kg

Length of penetrator rod: 480mm
Minimum diameter of the projectile rod: 34mm

Penetrator L/D ratio: 14.12:1


Penetration at 2000m:

430mm RHA at 0°
250mm RHA at 60°

(From plaque)


Certified penetration at 2000m: 

500mm RHA at 0°

250mm RHA at 60°



Penetration into spaced targets:


7-layer array at an angled of 60 degrees (630mm LOS) could be defeated at 3200 m.

7-layer array at an angle of 30 degrees (620mm LOS) could be defeated 3200 m.


3-layer spaced array at an angle of 65 degrees (1830mm LOS) could be defeated at 5000 m.




The photo below shows a 120mm DM13 APFSDS shell made for the Leopard 2. It was introduced in the same year as the Leopard 2; 1979.



1. Steel windshield and ballistic cap 2. Steel ballistic cap 3. Tungsten penetrator 4. Steel sheath 5. Tailfins and tracer assembly


As you can see, the resemblance is striking. The dimensions are also quite similar, and so is the mass - 4.85 kg for the Vant, and 4.6 kg for DM13. Form follows function, of course, and the "Vant" being a jacketed long rod projectile meant that it didn't have many forms to choose from anyway. What is especially remarkable about the DM13 is that its tungsten penetrator is only about 240mm in length and the front half of the projectile is just plain steel, but apparently, that does not prevent it from penetrating 230mm RHA at 60 degrees at a distance of 2200 m. The 105mm DM23 was introduced years later in the early to mid-80's, and had a longer tungsten alloy core, with a better L/D ratio, and yet it offered much worse performance. Why? How? Maybe it is better not to ask...


"Vant" is approximately comparable to the American M829, which began production in 1984 and entered service in the same year as the Vant (1985) to equip the freshly inducted M1A1 Abrams tank. M829 is only 30 m/s slower than Vant at 1670 m/s, but M829 loses less velocity over distance due to its small, subcaliber fins and had a longer 540mm-long sheathless monobloc DU penetrator capable of penetrating approximately 275mm RHA at 60 degrees at 2 km.





3BM-44 (Mango)

3BM-42




Developed in parallel with "Vant", "Mango" is a more advanced counterpart using tungsten instead of depleted uranium. The 3BM-42 projectile has a two-part tungsten alloy penetrator, but technically it is a three-part penetrator, as the rod supplemented by a 112mm tungsten alloy segment at the tip with a diameter of 22mm - greater than the diameter of the main penetrator. The penetrator is encased in a thin steel jacket which holds the two long rod penetrators together.

It is commonly thought that the two-part penetrator rod was used instead of a single rod because the technology was not yet mature enough to produce a single full length rod, but if that is the case, then it is a mystery why the Germans designed the DM13 to have a steel segment in front of its tungsten long rod penetrator instead of simply putting two tungsten rods together.




Since one of the long rod penetrators in "Mango" is shorter than the other, it is unclear why the shell is not longer than it is, as it should not be difficult to have two long rods instead of one long rod and one short rod. From various studies on the behaviour of long rod tungsten alloy penetrators on spaced armour and thin oblique plates, it is very likely that the short tungsten alloy segment at the tip of the projectile will prevent the rest of the rod from breaking up after perforating a spaced armour plate at high obliquity, or at least control the damage in such a way that the rest of the rod will penetrate any further armour plating with greater efficiency. The use of a separate tungsten alloy segment at the tip of the projectile was definitely a deliberate design solution meant to counter non-homogeneous armour, as there would be no limitations against producing a simple flat tip or a frustum for the shorter half of the two-part penetrator.

The segment at the tip is only partially jacketed, and is therefore largely separate from the rest of the projectile, so the damage sustained by the segment will be mostly isolated from the rest of the projectile. This will protect the integrity of the jacket, and thus preserve the performance of the projectile against a spaced or composite armour array behind the initial front armour plate. As the armour of both the Abrams and Leopard 2 are understood to rely on an array of NERA and steel armour plates, the effectiveness of "Mango" could be quite high despite the less technically advanced nature of the shell. The shorter half of the two-part penetrator is at the front, and may possibly give "Mango" the ability to counter dynamic protection such as Kontakt-5, besides generally improving its effectiveness against NERA.

German military expert, author and lecturer Rolf Hilmes has said that the German 120mm DM53 is specially constructed to deal with advanced composite armour and dynamic (reactive) armour. Its construction, he says, consists of a three-part tungsten alloy penetrator. If having multiple segments is a valid method of overcoming complex composite and reactive armour, then "Mango" may be an example of "taking one step back but two steps forward". Of course, it should be stated that "Mango" is not nearly as advanced as DM53. It is simply interesting to note that the design of "Mango" has more in common with the latest anti-tank ammunition than the ammunition of its time. One of the features of "Mango" that may potentially make it more suitable against non-homogeneous armour is the steel jacket over the tungsten alloy penetrataor rod, same as "Vant".


Photo from soviet-ammo.ucoz.ru


As mentioned before, it is known that jacketed penetrators perform substantially better against spaced armour and may have better performance than monoblock ones against certain types of composite armour. The weakness of jacketed long rod penetrators is its reduced penetration power against homogeneous steel armour, as detailed in "Numerical Analysis and Modelling of Jacketed Rod Penetration". The paper reveals that decreasing the thickness of the steel jacket relative to the diameter of the (depleted uranium) rod to a ratio of 0.1 results in the smallest degradation of penetration against steel armour, but the steel jacket for 3BM-42 is rather thick - much thicker than on the 3BM-32. The total diameter of the projectile at the middle is 36mm, but the tungsten alloy core is a mere 18mm in diameter, meaning that the jacket is 9mm thick. This is verified by the photo below, taken from Andrei Tarasenko website, btvt.narod. 





Having such a thick jacket, the bulk density of the projectile is much, much lower than a monoblock tungsten alloy rod, but this is compensated by the high overall mass of the projectile of 4.85 kg, which is identical to 3BM-32 and compares favourably to the 4.6 kg of the 120mm DM33, which had a slightly lower muzzle velocity of 1650 m/s.

On the other hand, some sources state that the jacket on 3BM-42 is supposed to melt away upon impact to allow the tungsten alloy rod(s) to pass into the target without expending energy to separate itself from the jacket. This simply cannot be true, and the reason should be quite obvious at this point.


The 3BM-42 projectile is generally similar to the 3BM-32 in external layout due to the use of a similar "bucket" type sabot, but the projectile is significantly lengthier. The sabot is made out of a light V-96Ts1 aluminium alloy, helping to decrease parasitic mass and thus increase firing efficiency. The driving bands are made from plastic and help reduce barrel wear, although it is still quite high due to the high pressure of the shell. The long-rod tungsten alloy penetrators are encased by a thin sheath made from S-7 impact-resistant tool steel. It is known that jacketed or sheathed long rod penetrators have superior performance on composite armour arrays, because the sheath protects the rod from external perturbations and keeps it intact as the projectile passes through the array.


"Mango" in the possession of a lucky individual

As you can see clearly in the photo above, "Mango" still has bore riding fins. The copper-coloured nubs on the apex of the fins you see above are copper ball bearings. Larger fins create more drag, leading to a lower velocity downrange.


The dimensions of 3BM-42 come from the table below. Original source unknown.


Muzzle velocity: 1715m/s

Mass of sabot: 2.2 kg
Mass of projectile only: 4.85 kg

Length of projectile only: 574mm
Diameter of projectile: 31mm

Length of two-part core: 420mm
Length of tungsten alloy armour piercing cap: 112mm
Diameter of core: 18mm
Diameter of tungsten alloy armour piercing cap: 22mm

Penetrator L/D ratio: 20:1

Chamber pressure with
Zh40/Zh52:  443.8 mPa
Zh63: ?

EFC rating: 5


Certified penetration at 2000m:

450mm at 0°
230mm at 60°

(From Fofanov's website)


Penetration into spaced targets:

7-layer array at an angled of 60 degrees (630mm LOS) could be defeated at 3300 m.

7-layer array at an angle of 30 degrees (620mm LOS) could be defeated 3800 m.

3-layer spaced array at an angle of 65 degrees (1830mm LOS) could be defeated at 2700 m.


Without knowing more specific details regarding these armour arrays, we cannot know how correctly they represent NATO armour at that time. It is very likely that the armour of the M1 Abrams will be defeated effortlessly by "Mango" at combat distances, since we now know the layout of the armour and some details of the steel plates it uses. It is very possible that M1A1, which had a thicker array, can be still defeated by 3BM-42 at short range. Based on the limited information currently available, the Leopard 2A0-A4 is probably more resilient to 3BM-42.



ATGM


3UBK14 

9K119 "Svir"





The 9K119 "Svir" is a guided missile with a single 4.2 kg shaped charge warhead designated 9N142. The missile achieves excellent armour penetration with a limited length and warhead diameter thanks to the placement of the warhead at the rear of the missile, thus creating a large amount of standoff distance without the need for a special standoff probe.

The missile is soft-launched by a 9Kh949 reduced load piston-plugged ejection charge, giving the missile some momentum before the rocket motor kicks into action. The piston plug is designed to properly seat the missile in the chamber, but its primary purpose is to protect the laser beam receiver at the base of the missile from propellant gasses. The total weight of the 9Kh949 charge is 7.1 kg.




The missile itself has an efficient layout with the rocket motor placed in the middle, the warhead at the very rear, and the control surfaces and mechanism at the front along with the fuse at the tip. The large distance between the fuse at the tip of the missile and the warhead gives the warhead a good standoff distance without the need for a special standoff probe. The layout enables the 125mm missile to have a comparable flight range as the 127mm ITOW missile, and superior armour penetration performance, but in a much more compact package. With 700mm of penetration, "Refleks" is a much more serious weapon with a much better chance of defeating the new generation (at the time) of NATO tanks like the Leopard 2 and M1 Abrams, albeit from the side. The chances of defeating such tanks from the front with this missile are rather slim.

The missile uses a solid fuel motor, with four nozzles arranged radially. Flight stabilization is maintained via five pop-out tail fins with curved and angled surfaces to impart a slow spin onto the missile, while steering is accomplished by the two canard fins at the front. These are operated pneumatically, so the more corrections the gunner makes while the missile is mid flight, the less responsive the missile will be over time, though the gunner will have to be tracking a very difficult target like a moving helicopter for this to become noticeable.



Guidance is accomplished by the integrated 9S517 modulated laser beam unit on the 1K13 sighting complex. The system has a maximum range of 4000 meters.





Missile Diameter: 125mm
Missile Length: 695mm

Wingspan (Stabilizer Fins): 250mm

Firing Distance: 100 - 4000 m

Penetration: 700mm RHA

Hit Probability On Tank-Type Target Cruising Sideways At 30 km/h:
100 m to 4000 m =  >90%

Flight Distance Time:
4000 m - 11.7 s


The "Svir" missile was the longest ammunition type available to the T-72 before the end of the Cold War. This fact is illustrated by the photo below (although the missile shown in the photo is a 9M119M).





3UBK20 "Invar"

9M119M


"Invar" is a follow-up to the "Svir" missile. The main improvement is in the rocket motor, giving the "Invar" an additional kilometer of flight range over its predecessor, but the missile also features a new 9N142M tandem warhead. Externally, it is identical to its predecessor. "Invar" was introduced in 1989 and is currently in service in the Russian ground forces.


Firing Distance: 100 - 5000 m

Armour Penetration:

700mm RHA

(Rosoboronexport)



PKT



The PKTM is mounted as a co-axial machine gun, with 250 rounds readied per box and with 8 boxes carried in the stowage bins on the outside of the tank and inside as well. Ball and tracer ammunition are usually linked in a 2:1 ratio, though sometimes tracers are used exclusively. The theoretical maximum effective firing range is 650 m against a running target, and up to 1500 m against stationary targets. However, the actual practical ranges are much lower at around 600 m for both running and stationary targets, depending on terrain and meteorological features. The gunner's ability to actually see and track personnel at extended ranges also plays a huge part in the co-axial's practical engagement envelope.


It is fired by the gunner using his "Cheburashka".

Notice the cable leading away from the PKT to the left



The machine gun is mounted to the right of the main gun, and protrudes from a pill-shaped port which provides vertical space for gun elevation. Since it is mounted alongside the main gun, it receives all the benefits of the stabilization system.


The co-axial machine gun is only a limited solution to the infantry problem, especially if hard cover is available. In practice, the co-axial is only useful in very specific situations, and desirable only when HE-Frag shells are not suitable due to concerns of collateral damage or (more brutally) when the concern is ammunition wastage. In essence, the PKTM is more of a weapon of opportunity than anything else.

 


ANTI-AIRCRAFT MACHINE GUN





The T-72 has a heavy machine gun for the commander mounted on the ZU-72 mount with an NSVT heavy machine gun. The machine gun is primarily intended for the anti-aircraft role, though it may be used to shoot at ground targets too. The ZU-72 mount has a range of elevation of -5° to +75°. The cantilever mounting of the machine gun is balanced by a pair of springs affixed near the center of gravity of the machine gun.




Rotating the cradle and elevating the machine gun is done manually, and firing is done by squeezing a trigger paddle on the left handle. The machine gun is traversed left and right by simply moving the cupola using body weight, and the elevation of the machine gun is manipulated by working a flywheel located to the right of the machine gun. The commander has to stand on his seat in order to reach the machine gun. The elevation flywheel has a braking button. The brake is used to hold the machine gun at a fixed elevation while shooting to ensure better accuracy. If the brake is not activated while shooting, the machine gun may experience overwhelming muzzle rise due to the cantilever mounting of the machine gun.

As mentioned before in the "Commander's Station" section, the machine gun is mounted on a race ring that can spin independently from the rest of the cupola, thus allowing the commander to fire the machine gun with a modicum of frontal protection from the hatch.




Unfortunately, the IR spotlight prevents the machine gun from being aimed when it is traversed to directly in front of the cupola, although it is possible to traverse the machine gun 360 degrees by elevating it to its maximum elevation to clear it from the IR spotlight. In the travelling position, the race ring for the machine gun mount is locked to the fixed turret base by a spring loaded plunger, marked '18' in the diagram below. The inner cupola - which carries the commander's optics and hatch - runs on a smaller race ring along the intermediate band.




When not in use, the machine gun is kept in the travel position, meaning that the inner cupola rotates without bringing the machine gun along, making it lighter and easier to spin around and survey the battlefield. When the plunger locking the intermediate band to the fixed base is released, the machine gun is allowed to traverse freely along the race ring between it and the fixed base. The inner cupola may be locked to the intermediate band or left free. In the former case, the cupola rotates with the machine gun, so spinning the machine gun to face the front would spin the cupola to face the rear. This is the normal combat procedure, because it gives the commander complete access to the machine gun and allows him to reload it more easily. In the latter case, the position of the machine gun relative to the cupola can be changed as the commander wishes. It is possible for him to open fire on either side of the turret (at strafing aircraft, for instance) while keeping the cupola facing where bullets are expected to come from.


The machine gun is complemented with a K10-T collimator sight, which facilitates aiming at both ground level and high altitude targets. It is tinted to reduce glare when aiming in the direction of the sun.






Using the collimator isn't compulsory. If it is damaged or unsuitable, the iron sights on the machine gun may still be readily relied upon.  

Hungarian Ron Swanson aiming through such a sight

View through the sight
The collimator projects a clear, crisp aiming reticle


The machine gun has a nominal effective range of approximately 800 meters against aerial targets, but this is variable. Obviously, the probability of hitting a hovering helicopter would be much higher than hitting a moving fixed-wing aircraft.




As a rule, anti-aircraft machine guns (AAMG) are more or less useless for shooting down aircraft. Although it isn't difficult penetrating some of the more obvious weak areas such as the plexiglass windscreen on a helicopter, the chances of actually hitting a fast, moving target is rather slim. On the contrary, the role of an AAMG is to be a deterrent; it's objective is to "shake up" the pilot(s) into pulling back from an attack, or perhaps even make him miss his shot. Serious anti-aircraft work is to be carried out only by the SHORADS (Short Range Air Defence Sytems) accompanying the T-72.

The machine gun is fed from a 60-round box, holding a mix of B-32 API and BZT API-T ammunition. Four additional boxes of ammunition are stored in metal bins in the turret and two more are strapped to the outside of the turret, which the commander can reach down and access while he is operating the machine gun. The commander has to pull a large charging lever to cycle the gun (pictured below).




The lack of a remote aiming and firing system for the machine gun like on the T-64 has been said to be one of the greatest drawbacks of the T-72, and for good reason. Former Russian tank crews who served in Chechnya mentioned that it was suicidal to man the machine gun when in combat, so despite its high power and high rate of fire, the NSVT is not suitable for suppressing manpower in urban environments. Tank crews in Syria have also never been observed to use the machine gun during urban combat, for the same reasons. It is interesting to note that Leonid Kartsev defended this design decision in his memoirs, stating that it helped to have an unobstructed field of view when firing at aircraft, but this is a rather weak argument, since the commander of a T-64 could fire his NSVT from outside of his hatch as well if he desired. It was no coincidence that the ZU-72 anti-aircraft machine gun mount was replaced with a remote control system in the T-90.




Due to length restrictions, this article has been divided into two parts. Part two is available here.