Russo-American Tank Destroyer

One of the key problems with using foreign tanks is keeping a steady supply of spare parts and ammunition. This problem is not exclusive to captured tanks. A similar situation often took place with vehicles that were sent willingly. For example, a lack of ammunition delayed the arrival of American tanks on the battlefields of the Eastern Front by several months. These shortages happened more than once. It is not surprising that arming foreign tanks with domestic guns was a frequently suggested solution.

S-1 (SU-76I), the first design of the TsAKB. The bureau had some experience in re-arming foreign chassis.

It just so happened that the best results in rearming foreign tanks were achieved by the design bureaus of factory #92 and factory #592. The first only offered experimental solutions, but the latter built a small batch of SG-122 SPGs. Specialists from both bureaus were later united in one organization: the Central Artillery Design Bureau (TsAKB). Their first project, the S-1, was a part of rearming a foreign tank (SU-76I). It’s not surprising that new rearmament projects followed, including grassroots proposals.

The second wave of Sherman tank shipments began in late 1943. This likely kickstarted Chasovnikov’s initiative.

Rearming foreign tanks and SPGs was not a priority for the TsAKB, but it was not uncommon. This was not always grassroots work. For instance, new armament for the Valentine tank (likely the Valentine V) that was developed in April of 1944 was ordered from above. This was not just a 45 mm gun, but the 85 mm S-53. Given the size of this gun and the size of the Valentine V turret, the GBTU must have had its share of optimists.

Chasovnikov’s proposal was sent to the commander of the Armoured Forces, General-Colonel Fedorenko. The work was seriously discussed at the highest levels.

The reasons for this prelude will become clear. A wide variety of people worked at the TsAKB including engineer-designer A.S. Chasovnikov. Sadly, details about his fate are unknown, but he had a storied past. His inventions include various devices for offloading tanks during travel by rail and attachments for camouflage. He was no stranger to the front lines. In the summer of 1941 he served in the 53rd Tank Regiment of the 81st Motorized Division. His camouflage device was used on some vehicles and received positive feedback from crews. However, the GABTU did not appreciate this design. It’s hard to say why he idea did not gain traction. Many nations, for instance Sweden, used similar devices to hide their tanks with branches.

The conversion was very thorough.

Chasovnikov’s specialty in the TsAKB was the rearmament of tanks. This work didn’t just stay on paper. The installation of the S-53 gun into the KV-1S (S-28) was his doing. It’s not surprising that in January of 1944 Chasovnikov and S.D. Kazarin (another engineer from the TsAKB) presented a series of proposals to rearm foreign tanks. The main argument was that foreign tanks had weaker guns than domestic ones. The Red Army had just accepted the 85 mm D-5T-85 and S-53 guns into service. Factory #112 began building the first T-34-85 tanks and factory #183 was getting ready to produce T-34 tanks with the S-53 gun. This was indeed a more powerful weapon than foreign tanks carried.

The Matilda was also a candidate for conversion.

Several different solutions were offered. The first was a simple replacement of the main gun with an 85 mm weapon. The M4A2’s turret was a good fit for this. A second alternative was the replacement of the whole turret with that of a T-34 tank carrying an 85 mm gun. This turret would be used on T-34 tanks built at factory #183. However, the tank remained a prototype and the T-34-85 that entered production at factory #183 in March had a new three-man turret on a 1600 mm turret ring. The most interesting proposal was the third option: converting the vehicle into an SPG. The Sherman was once again chosen as the subject. The Matilda was listed as an alternative, but the authors did not develop it in detail. This is most likely because it was not a simple as slapping on a new casemate and would have needed a lot more work.

The conversion was fairly high level.

The work on the M4A2 was done in more detail. The idea was also more practical. According to the description, the turret and turret platform were removed. A gun port was cut out in the front hull which housed a gun mount similar to that of the SU-85. A new roof was installed over top and voila, a new tank destroyer analogous to the SU-85 was born. The amount of work this required was comparable with what was needed to built the SU-76I. The inside became a bit cramped but the gun fit. The gun didn’t need a pedestal like the M-30 in the SG-122. The gun was fitted into a frame that was bolted to the front armour.

The TsAKB already had the 100 mm S-34 gun. It was considered the favourite in early 1944.

It’s worth mentioning the armament installed in the converted M4A2. The D-5T-85 gun was the priority and this was the gun that was shown in the drawings. However, Chasovnikov and Kazarin also described the possibility of installing a 100 mm gun. They already knew about the 100 mm S-34 gun that the TsAKB created for installation into the SU-100. The layout of this gun was preferable, as the gunner sat to the right and would not get in the driver’s way. Following Soviet naming conventions, this vehicle would have been called SU-100I.

The vehicle could have been called SU-100I

However, Chasovnikov and Kazarin’s idea was declined at a meeting held on February 15th, 1944. One of the opponents of the proposal was S.G. Pererushev, one of the developers of the SG-122 and SU-76I. The proposal was sent off to the GBTU Department of Inventions, a dumping ground for death rays and perpetual motion machines. However, this didn’t mean that the TsAKB was necessarily rejecting the idea but rather passing it off as a grassroots initiative. 

The proposal ended with nothing

Engineer-Major Goncharov (Sr. Assistant to the Chief of Department of Inventions, GBTU KA Technical Directorate): The proposal is not serious, baseless, and unclear to the authors themselves. It has a very single-minded approach. The authors proposed converting foreign tanks into SPGs, then replacing the turret, and finally replacing the gun. It seems as though the authors were dead set on replacing or changing something no matter what. Changes and replacements cannot be a goal unto themselves but must have clear reasons. In this case there is no reason to make the rearmament and replacement in large numbers. If rearmament is made, foreign guns will be replaced with domestic ones in cases where it is justified but independently from the authors’ proposals and designs.

Guards Colonel Kulnitskiy (Assistant to the Chief of the GBTU Technical Directorate): Out of all the proposals made by the authors, one can only speak of the gun replacement. It is not necessary to limit oneself to the 85 mm gun. As some comrades already mentioned guns are replaced when tanks are repaired. Raising the issue of rearming the M4A2 with an 85 mm gun is senseless as there is a shortage of these guns. We can’t even rearm domestic tanks for this reason.

Comrade Chasovnikov (proposal author): I see now that the issue of replacing the turret or converting the M4A2 tank to an SPG is unrealistic. Now I agree.

As for the rearmament of M4A2 tanks with an 85 mm gun, I think that a portion of the tanks should be rearmed. A technical project should be prepared and a prototype built. Then we can decide whether or not to move forward. My opinion is based on the fact that the M4A2 is good in all respects and the only weak point is its armament. If we put an 85 mm gun in it, it will be irreplaceable.

To conclude, let us mention that some ideas are contagious. In our time some scale modellers built their own tank destroyers on the M4 chassis. However without an engineering education, these designs are entirely unworkable. 

Original article by Yuri Pasholok