Thursday 28 March 2013

GABTU's Answers to the Tiger

In 1943, Tigers were deployed in sufficient numbers to become a nuisance to the Red Army. The Head Armour and Tank Directorate (GABTU) issued a set of requirements to increase effectiveness against heavily armoured tanks.

CAMD RF 38-11355-1380

"On the subject of combating German heavy tanks, the State Committee of Defense has established that:
  1. NKV (comrade Ustinov), GAU KA (comrade Yakovlev), head of the TsAKB (comrade Grabin), director of factory #8 (comrade Fradkin), and the head engineer of factory #8 (comrade Sandler) must:
    1. Increase the penetration of the 85 mm tank gun, such that it penetrates 100-110 mm of armour at 2000 meters. Present a prototype to the Kirov factory by June 15th, 1943.
    2. Design and manufacture a 100 mm tank gun with a two piece shell that can penetrate 120-130 mm of armour at 2000 meters.
  2. The People's Commissariat of Munitions (comrade Vannikov) and GAU KA (comrade Yakovlev) must:
    1. Shortly, no later than June 1st, 1943, begin the manufacture of 57 mm HE shells.
    2. Shortly, no later than June 1st, 1943, design a new AP shell for the 76 mm F-34 gun that can penetrate the side of a Tiger tank at 600 meters.
    3. Shortly, no later than June 15th, 1943, develop a subcaliber round for the 76 mm F-34 gun, capable of penetrating the front of a Tiger tank at 500 meters.
  3. The People's Commissariat of Tank Manufacture (comrade Zaltsmann) must:
    1. Starting on May 15th, 1943, install a 57 mm tank gun (ZiS-4) on 2-3 out of 10 T-34 tanks.
    2. By June 1st, 1943, build 3 prototypes of a self propelled 57 mm gun on the T-70 chassis (SU-57). The prototypes will be tested by the GAU KA in ten days from their arrival, and the result will be delivered to the GSKO.
    3. By June 1943, develop a tank destroyer on the SU-152 chassis armed with a 122 mm gun model 1931, and manufacture an equal number of these new TDs as the SU-152.
    4. By July 1st, 1943, develop a tank destroyer on the T-34 chassis with an 85 mm tank gun (SU-85) with a rear fighting compartment, like the SU-76."
Quite a number of requirements! Let's go through them one by one.

Factory #8 is tasked with developing new 85 and 100 mm guns. The experimental high power 85 mm gun in a penetration table from 1944 penetrates 89 mm at 2000 m. Not quite there. The existing 85 mm gun was quite effective against Tigers, so it's understandable that the high power gun was not deployed. As for the 100 mm gun, the D-10 is capable of penetrating 125 mm of armour at 2000 meters. This requirement was met.

57 mm HE shells? Against a Tiger? Well, of course not. The 57 mm HE shells were meant to make the T-34-57 (which the Soviets had since 1941, but didn't really see an opponent worthy of their high penetration guns) into a platform as versatile as the T-34-76, useful against both infantry and tanks. Since T-34-57s were built in very small numbers, it's safe to assume that even if Vannikov and Yakovlev were successful, their efforts were in vain. 

As for effectiveness against a Tiger from the side at 600 meters, the engineers only managed to ensure effectiveness at 500 meters. Many efforts to develop a viable subcaliber 76 mm shell were made, but the same penetration table only gives 92 mm of "guaranteed" penetration. I guess that number would be around 100 for "initial" penetration, so that's another checkmark. 

As I mentioned before, there was a very small numbers of T-34-57s developed, and even fewer saw combat, so the 20-30% figure was not achieved. However, since T-34-85s rolled off the assembly lines, 100% of T-34s were able to face a Tiger at long range, instead of 30%.

A SU-76 with a semi-automatic 57 mm gun was requested, and may have even been tested, but not deployed. The SU-76 was effective against infantry first, and tanks second, and a 57 mm gun would jeopardize that. The SU-57 index ended up assigned to an American Lend-Lease halftrack that mounted a 57 mm gun.

A SU-152 with an A-19 gun was never fielded, but the ISU-122 was the same thing, but on the ISU-152 chassis.

The SU-85 was, of course, mass produced, but not with a rear fighting compartment. Engineers chose the more proven design of the SU-122, with a front fighting compartment. The same design was used for the SU-100, with the aforementioned 100 mm gun. 

1 comment:

  1. The hesitation to adopt higher alloyed steel for AP projectiles with decremental hardening, armour piercing and ballistic cap was a missed opportunity here. The exiting stock of large number of 76mm ATG could be updated to cope with TIGERs if such a step had been taken.

    That it was possible to do so is demonstrated by the fact that the germans captured a large number of soviet 76mm tank- and anti-tank guns and manufactured their own 76mm AP projectile for their outfit -partly because the captured stock of soviet 76mm was considered not satisfactory in term of AP-performance, particularely againt high hardness plate or close range.

    The re-engineered (german) higher alloyed 76mm PzGr 39 APCBC projectile design was proof tested to perforate 100mm RHA (95-105kg/mm^2 tensile strength) five out of five times (no failures allowed) at 30° obliquity and 740m/s velocity. Rated performance in explorative trials was 107mm RHA at 30° and 125mm RHA at 0°. Sufficient to penetrate the TIGER I´s sides out to distances in excess of 1500m.