The Hybrid Tank that Led to the T-34-85

There are many cases in history where a tank that remained a prototype helped out another one that went into mass production. In part, this happened with turrets which lost their chassis but found a new home on another tank. Sometimes whole new tanks grew out of the turret, like the Pz.Kpfw.IV. These "centaurs" often grew into true workhorses that were built in huge numbers and remained in service for decades.

A T-34 tank with the T-43 turret, fall 1943.

Two such turrets came into being in 1943. One was the result of work on the Medium Tank T23, a prospective vehicle that was supposed to replace the Medium Tank M4. The replacement didn't pan out for a number of reasons but the turret came in handy when developing the Medium Tank M4(76). A similar thing happened in Soviet tank building. Trials of the turret taken from the second T-43 variant and transplanted on top of a T-34 tank led to the creation of the T-34-85.

Two tanks were converted: one had a 76 mm F-34 gun, the other the 85 mm D-5T-85.

One can read about many reasons for why the T-43 didn't go into production, some of which don't pass any scrutiny. In reality, the tank simply couldn't keep up with growing requirements. This became clear after the end of the Battle of Kursk where the Germans deployed a number of new armoured vehicles. The order to install the 85 mm D-5T-85 gun into the T-43 came right after the battle. A dummy gun was installed in September of 1943, showing that this upgrade was possible. However, the requirement to increase the armour to 90 mm was impossible. The tank's weight would increase to 35 tons.

The 85 mm gun was a higher priority.

The situation around the T-34 was even worse. Work on the 57 mm ZIS-4 gun resumed in the spring of 1943 when it was needed once more. Trials against Tiger tank #121 showed that the 76 mm gun doesn't penetrate the armour of the German "beast" even at point blank range, unlike the ZIS-2. However, Panthers turned up at the Battle of Kursk, which put a pause on the ZIS-4 too. To replace it, work started on the 76 mm S-54 gun, a descendant of the 3-K AA gun. Even this gun was a half-measure.

This work showed the T-43 in a new light. The chassis was still a dead end, but the turret was a lot more interesting. The wider turret ring that the GBTU insisted on helped the conditions of the tank's crew. The trials commission did have its complaints: the commander's seat needed a back, the gunner slid off his seat to the left when the tank was moving, and the loader had no seat or even a perch, plus he his his head on the torsion bar that balanced the hatch. Nevertheless, there was a positive effect. The rate of fire of the F-34 gun improved to 13 RPM compared to 10 RPM in the same conditions on the T-34. Observation from the T-43 turret was also better.

The tank was tested at the Gorohovets ANIOP between November 20th and November 23rd.

As a result, in the fall of 1943 the Red Army had a chassis with an obsolete turret and a future-proof turret from a useless tank. After the D-5T-85 gun showed itself well in the T-43's turret the idea of transplanting the turret from the T-43 to the T-34 was finalized. The problem wasn't that the turret ring had to be enlarged to 1600 mm as you can sometimes see claimed, but rather that the result of the transformation would be a temporary drop in production numbers. This is why KB-520 and A.A. Morozov personally fought against the idea to the point where the T-34-85 initially put the 85 mm gun into the two-man T-34 turret. This turret was accepted into service by GKO decree #4873ss issued on January 1st, 1944. This wasn't a T-34-85 turret on a narrower turret ring but rather an ordinary T-34 hexagonal turret.

There was opposition to putting this tank into production.

The work to convert two prototypes to take the T-43 turret was opposed by factory #183, even though the "T-34 tank with a 1600 mm turret ring and an 85 mm gun" was the first on the approved projects plan as of October 1943. The GBTU requested documentation in November of 1943, but in Nizhniy Tagil documentation lagged behind work in metal. It was expected by November 27th while the tanks with T-43 turrets were ready much sooner.

The T-43 turret was too heavy for this chassis.

It was not that hard to replace the turret. All it took was a new turret platform with reinforcements on the sides of the hull. The radio operator's station was also altered. He was only left with the bow gun, as the radio was moved to the turret for the commander to use. The antenna was also moved to the turret and the port in the hull was welded up. The second tank was built with an F-34 gun but this was more of a backup plan. The D-5T-85 was the much more promising option.

Fighting compartment layout.

While factory #183 was busy with finishing their paperwork, the prototypes went out for trials. The trials took place at the Gorohovets ANIOP between November 20th and November 23rd, 1943. The trials commission was headed by Colonel Ye.A. Kulchitskiy. It contained representatives of the GAU, GBTU, and NKV as well as two representatives from the NKTP and P.F. Muravyev, one of the lead engineers from TsAKB. His presence was no accident. The TsAKB quickly saw the value of the new turret and build new guns specifically for it. The S-53 was meant to go into this turret as well as the hexagonal two man turret from the beginning.

Vertical cross-section of the gunner's station.

A rate of fire of 6 aimed shots per minute was reached during trials. The effectiveness of fire against moving targets was tested as well and was deemed to be satisfactory. Trials showed that the ready rack was hard to reach while the rack in the turret bustle was actually the easiest to use. The effort on the aiming flywheels was high (8-10 kg to elevate the gun and 7 kg to turn the turret) but the most important thing was that there was plenty of room for the crew to work. The commission noted that three men would not fit in a turret narrower than 1600 mm.

The same tank with the LB-1 gun.

Of course, there were drawbacks, mostly assembly defects. The commission also recommended a pedal activated electric firing mechanism. Even so, the most important goal was reached. The new turret could fit a three man crew and a more powerful gun. In addition, observation from the T-43's turret was better than from the T-34. This turret was recommended for mass production after improvements were made, but this never happened. For one, the turret was much heavier than the hexagonal turret and a lighter version would have to be developed. The other issue was that the turret with a widened turret ring was only considered to augment production of the T-34 tank with the 76 mm S-54 gun. In other words, there were still concerns about a drop in T-34 production.

This turret was never mass produced, but it served as the foundation for a new T-34-85 turret designed at factory #112.

This is why the S-53 gun appeared in the stock T-34 turret. It was tested between December 26th and December 31st, 1943. The T-43 turret also served as a test bench for the LB-1 85 mm gun. Neither gun passed trials, but the S-53 was deemed more promising. The commission once more pointed out that the enlarged turret was better. The T-43 turret on the T-34 tank remained a prototype. A completely different tank went into production at factory #112. It had a new two-man turret and a D-5T-85 gun. This didn't last for long and T-34-85 tanks with S-53 guns and three man turrets entered production at factories #112 and #183 in March of 1944.

Original article by Yuri Pasholok.