K-91 World of Tanks Fake Version

Soviet Union (1949)
Heavy Tank – Fake

In the years that followed the end of the Second World War (Great Patriotic War), the Soviets designed a vast amount of armored vehicles. Some were mass produced in the tens of thousands, while some never left the drawing board and were buried in archives and drawers for decades. An example of the latter are the K-91 tanks designed by OKB IC SV (Design Bureau of the Engineering Committee of the Armed Forces) in 1949. These were only rediscovered in the late 2000s, and published in a magazine for the world to see in 2013.

When searching for vehicles to fill up a third line of medium tanks for their game World of Tanks (WoT), video game company Wargaming decided to take a controversial approach for their tier 10 vehicle, mashing up two different K-91 designs.

Background

There were three proposals designed simultaneously by OKB IC SV. Development started after the Council of Ministers of the USSR released decree No.701-277§ on 18th February, 1949, which requested the termination of all development and production of heavy tanks weighing 50 tonnes and above. This allowed OKB IC SV, headed by Anatoly Fedorovich Kravtsev, to design a set of vehicles aiming to take advantage of this opportunity. They were supposed to be lighter than 50 tonnes and be able to replace both existing and future medium and heavy tanks. Lead engineer was I.T. Levinov and the designer was Matyukhin. They designed three vehicles: a classical heavy tank, with a front mounted turret; a rear mounted turret heavy tank featuring an autoloader; and a rear mounted casemate self-propelled gun.

World of Tanks Hybrid

In the summer of 2018, the company Wargaming announced a new line of Soviet medium tanks for their game World of Tanks. It started with the A-43 at tier VI, and moved up to the A-44, Object 416, Object 430 II and finally, at tier X, the K-91. This line was set to have as the main feature rear-mounted turrets. The Object 416 was, in fact, a tank destroyer (also called the SU-100M).

One of the biggest offenses present in this new line is the mashup of the K-91 variants. The vehicle is identical to the first K-91 variant, but has the turret moved to the rear, just like the second K-91 variant. Why this was done is bizarre, as the second K-91 variant would have fit well as the tier X vehicle.

Video Game vs Reality

World of Tanks provides a short paragraph on the supposed history of their K-91:

“The vehicle was developed by the Design Bureau of the Army Engineering Committee under the supervision of A. F. Kravtsev from March through August 1949. The tank was supposed to position a driver in the fighting compartment, as well as feature a 100 mm gun with an automatic loading system, and coaxial large-caliber machine gun. The plan was to mount the 12-cylinder opposed-piston turbo-diesel engine. The mounting brackets with ski-shaped supports were used as support rollers. Development of the project was discontinued at the blueprints stage in December 1949.”

While the text does not have any particular inaccuracies, it clearly describes the rear-mounted turret K-91 and avoids the fact that the vehicle is a mashup. They do state that the engine was turbocharged, which cannot be verified.

Wargaming got the details and statistics right for the most part. Since there are very few drawings of the K-91s, and they were never built, it is hard to prove when something is accurate or not.

In-game, the K-91 has a 100 mm D-46T. This is historically accurate. The gun was intended as a replacement for the wartime D-10T. Development of the gun began on 28th May 1948 and two prototypes were ready by 1949. However, the program was canceled that same year. Its ammunition weighed between 16 to 17 kg and had a muzzle velocity of 1,000 m/s. In-game, however, it has a muzzle velocity of 1,700 m/s, and the tank can carry 50 of them. In-game, it has +20° of elevation and -9° of depression. In contrast, the real drawings show that it had +20° of elevation and -3° of depression.

Most of the model is a historically accurate render of the rear turret-mounted K-91 heavy tank. The turret matches the original blueprints, as in it has a conical shape, with a bulge for the driver that sat in the turret, to the right of the gun. The driver had a pivoting driving station, so that he would always face the front of the tank, regardless of the position of the turret. This does pose some mechanical problems, so it is unclear if the turret could fully rotate. This has been replicated in WoT, as the turret can only turn 110° in each direction. The loader is placed right behind the driver. On the left side of the gun is the gunner and the commander. The commander has a small bulge in the turret roof for better vision across the turret. A DShK heavy machine gun is mounted to the right of the gun and on the roof, as per the blueprints of the original K-91 with a frontal mounted turret.

The hull also matches the blueprints of the real K-91, but that with a frontal turret and not the rear-turreted one. A large sprocket drives the tracks, which are guided by a set of skids under the hull. The suspension is unique compared to other Soviet medium and heavy tanks. It features small steel-rimmed wheels, individually sprung by torsion bars. Only the first and last torsion bars have two wheels, with dependent suspension, via a pivoting bogie.

To move the turret to the rear, the designers at Wargaming had to make some slight changes to the hull. Mainly, the entire engine compartment was moved to the front, with a direct connection to the final drive, essentially a swap between the engine and turret.

In terms of propulsion, Wargaming states that it used a V-64 engine outputting 860 hp. While the specific power of the V-64 is unknown, Wargaming’s claim is in the upper limit of what the engine could have given. The V-64 was a 12-cylinder boxer diesel engine. The term boxer comes from the layout of the pistons, which are placed horizontally. This allows for a shorter engine and a lower hull, but the engine is also wider.

The armor was significantly lightened from the real blueprint. In-game, the upper frontal plate is 140 mm compared to 200 mm, while the lower plate is 120 mm in-game versus 150 mm on paper. The turret is 160 mm at the thickest and 40 mm at the thinnest, while on paper it was actually 200 mm all around. This was most likely done to fit the medium tank narrative in the game, but the weight remains at around 45 to 50 tonnes.

Wargaming could have easily added the real K-91 rear turreted heavy tank, instead of the current mashup. While it did have a different hull and turret shape, it was very similar. The main difference was the use of an autoloader for the 100 mm gun. Wargaming already exploits a variety of autoloading systems within their game, and since there is no information on the speed of the autoloader, they could have easily played around with the rate of fire data, for a balanced vehicle in-game. This variant does also have slightly thicker armor, but Wargaming has already taken the freedom to downgrade the armor of the in-game K-91 compared to the real thing.

The historical rear-turreted version of the K-91 had a very peculiar hull shape, with a bullet-like shape when seen from above and no vertical angling. Wargaming completely did away with that, preferring to keep the more conventional hull from the front turreted K-91 proposal.

K-91-2

Strangely, Wargaming decided to add the real K-91 frontal mounted turret as a Tier VIII premium medium tank (premium tanks are tanks that can be bought with real money or alternative currency within their game) with a fully rotating turret. Fortunately, it is accurate to the real original design, and it is a good representation of what the real project might have looked like.

K-91 PT

In March of 2021, Wargaming announced the introduction of the K-91 PT, which is the K-91 SPG variant. The acronym ‘PT’ comes from the romanized version of the Russian word ‘protivotankoviy’, meaning anti-tank. This is not entirely historical, as such vehicles were mostly called SU or SAU, from Russian ‘Samokhodnaya Ustanovka’, essentially meaning self-propelled gun.

Conclusion

While it is amongst one of the least offensive fake tanks in World of Tanks, the version of the K-91 in-game is still a fake that could have been relatively easily avoided if they just used the second historical K-91 version. Other than that, Wargaming kept the vehicle fairly historically accurate, with the exception of removing large amounts of its armor to make it a medium tank.

K-91 Fake tank specifications
Total Weight, Battle Ready	45 to 50 tonnes
Crew	4 (Commander, Gunner, Driver, and Loader)
Propulsion	V-64 engine, 860 hp
Speed	ca 50 km/h
Armament	100 D-64T
Armor	200 mm frontal turret, 140 mm turret cheeks 140 mm UFP 60 mm hull sides

Sources

Technic and Weapons No. 9, 2013, M.V. Pavlov, I.V. Pavlov Domestic armored vehicles of 1945-1965
Yuri Pasholok on the Soviet STG – Status Report (ritastatusreport.live)
https://military.wikireading.ru/56371
K-91 – World of Tanks – tanks.gg
K-91 – Global wiki. Wargaming.net