"Record of proving grounds trials of part 34.29.1051 (driver's hatch), cast, mechanically finished
The commission consisting of:
- Representatives of factory #183:
- Deputy Chief Metallurgist comrade D.I. Apatov
- Deputy Chief of Department #520 comrade A.V. Kolesnikov
- Representative of Department #9 G.G. Ionga
- Representatives of the BTU:
- Senior BTU Engineer, Military Engineer 3rd Class, comrade L.M. Grachev
- Senior Military Representative at the Mariupol Ilyich factory, Military Engineer 2nd Class, comrade P.N. Burykin
- Military Representative at factory #183, Military Engineer 3rd Class comrade G.Ya. Yalyshev
conducted trials on March 23rd and 24th, 1941, at the Glubokiy Yar proving grounds according to the program composed by the factory and approved by the BTU and made the following conclusions:
- Rationale: order of Deputy Director of factory #183 comrade Makhonin dated March 20th, 1941
- Goal: determine the resistance of armoured component 34.29.1051 assembled with components 34.29.1052 and 34.29.1053 to ascertain suitability for production.
- Method of trials:
Trials were held using a model 1937 anti-tank gun firing 45 mm shells (blueprint 2-03347) from 50 meters at normal and at angles of 30 and 60 degrees.
Trials with a 76 mm gun were not held due to the absence of a reloading bench.
Shell velocity was determined using two Tsirsky timers connected in parallel. - Characteristics of the components under test:
4 driver's hatches (part 34.29.1051) cast from 8S (MZ-2) steel, thermally hardened and mechanically finished (hardness of part 34.29.1051 is 2.8-3.1) were assembled together with shutters (parts 34.29.1052, 34.29.1053) cast from 8S (MZ-2) steel, thermally hardened and mechanically finished (hardness of 3.5-4.0). The chemical composition is attached to this record. - Results of trials:
- The resilience of part 34.29.1051 (driver's hatch) under fire at normal meets requirements for 8S (MZ-2) cast steel.
Limit of partial penetration is 685-715 m/s.
Limit of complete penetration is 714-727 m/s. - The type of damage when penetrated is satisfactory. There is no spalling or splintering.
- Part 34.29.1051 (driver's hatch) containing 0.22% carbon showed a limit of complete penetration of 727 m/s and limit of partial penetration of 690 m/s. The same part with 0.20% carbon showed a limit of complete penetration of 714 m/s and limit of partial penetration of 685 m/s.
- Cracks were found after impacts in four cases:
- A second hit within 52 mm of the edge (part 34.29.1051 cast A-351-5).
- A third hit within 107 mm from the edge (part 34.29.1051 cast A-351-1).
- A third hit within 33 mm of the edge (part 34.29.1051 cast A-351-4).
- A fourth hit near the left and middle periscope well beams (part 34.29.1051 cast A-351-3). This can be explained by the small size of the part under test and small distances between impacts.
- The robustness of the design is good. The shutters do not jam or open by themselves when hit. Shutters are not torn off. In three cases of shutters being hit directly at maximum speed only one resulted in the shutter being torn off due to destruction of the hinges (casting A-351-3).
...
Conclusions:
Based on the above trials held on January 16th, 1941, at the BTU Proving Grounds (Chuguyev) (conclusion #6 dated January 28th, 1941) the cast driver's hatch can be considered suitable for mass production.
[signatures]
March 26th, 1941."