Monday 1 August 2022

Soviet Upgrade for an American Tank

Modernization of a fighting vehicle over the course of production is a normal phenomenon. This was not the case from the very beginning, but modernization rather than creation of whole new designs was the norm by the 1920s. In Soviet practice, a good example of this is the MS-1. The first and fourth series differ significantly, and even so the full plans for improving the characteristics of the tank were not realized as it had become obsolete and did not satisfy the military's requirements even with changes. The MS-1's successor, the T-26 light tank, shows a much fuller spectrum of modernization. It started out with two turrets, one with a cannon and one with a machine gun. The first major modernization took place in 1933, and the tank that was produced at the end of its production run differed considerably from the first vehicle. Similar processes were not unusual for tank building of the era.

The first M4A2 tanks arrived in the USSR in the fall of 1942, but true mass deliveries began closer to the end of 1943. By that point the tank's armament was a bit weak.

The most drastic modernizations came about during WW2. This is especially noticeable in German, American, and British practice. The USSR also had two notable examples: the T-34-85 and IS-2. When it came to the Germans, their medium tanks were altered most drastically for approximately the same reason as the Soviet T-26: the tank stayed in production for a very long time because there was no alternative. Requirements for tanks grew too quickly. For this reason, the Germans kept building the Pz.Kpfw.III for much longer than they wanted to, increasing the characteristics of the tank not only through production changes, but also through modernization of existing vehicles. The Germans were the biggest fans of upgrading old vehicles, but far from the only ones. The British Cromwell, Churchill, and Sherman tanks were also modernized in colossal amounts. Similar processes in Soviet practice also took place, but remained in experimental stages. It just so happened that it was easier for the USSR to build a new tank than to re-arm an old one, although there were exceptions to this rule.

T-34 tank with an S-53 gun. Engineers Chasovnikov and Kazarin clearly knew about this project and were inspired by it.

One of the issues that constantly cropped up when it came to tanks arriving in the USSR was the armament. This was an especially big problem with American tanks. Issues with ammunition supplies led to a 4.5 month lag between the arrival of the Medium Tank M3 and Light Tank M3 and their use in combat. The issue of rearming British Matilda and Valentine tanks was raised even earlier. This work was triggered by the same issues with ammunition. Work on this topic died down, but "shell starvation" reared its head again. This time, a shortage of 3" ammunition resulted in a significant delay in the debut of the GMC M10. A different issue arose in 1943: weak armament. This led the British to rearm their tanks and SPGs. Similar processes took place at the Central Artillery Design Bureau (TsAKB). In part, engineers A.S. Chasovnikov and S.D. Kazarin came up with proposals to rearm several tanks, including the American M4A2.

Chasovnikov was no dreamer. Rearming tanks was his specialty at TsAKB.

The idea of rearming foreign tanks did not come from thin air. This idea was the continuation of work the TsAKB conducted since 1941. It was experimenting first with 76 mm and then 85 mm guns installed in the T-34's turret. The bureau stated in no uncertain terms that existing tanks could be rearmed. It is also important to state that Chasovnikov was not a mad scientist with too much time on his hands. In correspondence dated 1944, he is named as the chief of rearming tanks. At least one of his projects (the 85 mm S-28 gun) was built in metal and passed trials. Chasovnikov had a very convenient position. When favourable, he could be identified as a TsAKB employee, if not, then it could be claimed that this was a grassroots project that the TsAKB was not affiliated with. This is exactly what happened here. 

A proposal to install the T-34 turret on an M4A2 chassis. The blueprint indicates that the tank uses an 85 mm gun, but the type is not specified.

The TsAKB's proposal first reached the GBTU in January of 1944. The proposal covered multiple vehicles. Its primary motivation was that their armament was obsolete and something had to be done. Chasovnikov and Kazarin considered the optimal solution to be installation of a T-34 tank turret with an 85 mm gun. This was not even a T-34-85 turret, but an ordinary T-34 turret with a 1420 mm wide turret ring. Even though installation was developed for several tanks (the Medium Tank M3, Medium Tank M4A2, Matilda, and Valentine), the designers considered the M4A2 to be the primary option, as it was the most modern foreign tank shipped to the USSR. This rearmament seemed reasonable. Later, the GBTU claimed that the M4A2's firepower was sufficient, but this was not exactly the case. The 75 mm M3 gun was more powerful than the F-34, but far weaker than the 85 mm guns.

Location of ammunition.

The conversion was simple. The turret and turret ring were removed and a T-34 turret ring was installed. The ammunition racks were also changed. Turrets could be taken from damaged T-34 tanks where the hull could not be repaired. Turret baskets were retained and held 18 rounds of ammunition. 64 additional rounds could be stored in the hull, including the panniers. The tank carried 82 shots in total. Spare M4A2 turrets could be used as fortifications. The type of gun was not specified. This could be the S-53 or some other type of gun, as the TsAKB had no shortage of designs to choose from.

Artist's impression of what the M4A2 with a T-34 turret and 85 mm gun could have looked like.

Chasovnikov and Kazarin proposed another project after initial discussion with the GBTU. In this case, the regular M4A2 was used, but the M3 gun was swapped for the S-53. This was a much more realistic substitution. The S-53 gun could be comfortably installed in a 1600 mm turret ring (especially since it was designed for the 1420 mm wide turret ring), and the M4A2's whopping 1750 mm was more than enough. There was also a proposal to convert the M4A2 into an SPG, but it was far too unrefined. To be fair, the other proposals did not look much better. This was one of the major reasons why work did not proceed any further.

A more realistic proposal with an 85 mm S-53 gun installed in the M4A2.

A meeting between representatives of the GBTU, NTKP, GAU, and TsAKB was held on February 15th, 1944. The TsAKB was represented by Chasovnikov and S.G. Pererushev, one of the authors of the SG-122 and SU-76I. The conversions were harshly criticized, and even Pererushev did not support this endeavour. All work was obviously ceased, but this story has a number of interesting nuances. First, the claim that Chasovnikov and Kazarin came up with this proposal on their own is strange. Both of them should have been punished for wasting resources like this, but this didn't happen. Chasovnikov was not only not punished, but put in charge of tank rearmament. Kazarin also didn't go anywhere. He spent another few decades at the Leningrad branch of the TsAKB (later TsKB-34). Secondly, the GBTU turned to the TsAKB to help them with rearming Valentine tanks in April of 1944. It would be strange to think that the idea was not in demand in January-February, but required in April. Thirdly, the second variant of rearmament was quite promising, and the first was not devoid of merit either. THe only problem was that no factory could have taken on the work. In other words, one can't call Chasovnikov and Kazarin mad scientists, especially since one of them kept working on projects like these in an official capacity.


  1. Hmm, why would one want to put the two-man T-34/76 turret, with the S-53 85 mm gun, which would make the turret even more cramped, on the M4A2?

    Why not fit the same gun to the original M4A2 turret, which would have the advantage of thicker turret armor to boot (76 mm turret front, 81 mm mantlet?).

    1. A new gun in the same M34 mounting was also offered as an option. I would have expected this route to be easier than trying to mate the T-34 turret and Sherman turret basket, but I'm sure they had their reasons. It's possible they would have changed their mind once time came to actually build a prototype.