"To director of factory #92, comrade Elyan
In response to letter #202/4571
RE: 400 mm self propelled mortar
- KV-1 tank mod. 1941:
- Total mass: 46,000 kg
- Mass of the turret with gun and ammunition: 7277 kg
- KV-1 tank mod. 1942
- Total mass: 48,500-50,000 kg
- Mass of the turret with gun and ammunition (75 mm welded): 7770 kg
- Mass of the turret with gun and ammunition (110 mm cast): 8700 kg
- KV-1S tank
- Total mass: 42,500 kg
- Mass of the turret with gun and ammunition: 7204 kg
KV-1 tank ground contact surface: 4400 x 700 mm
KV-1S tank ground contact surface: 4400 x 650 mm
Experience when using KV tanks showed that a 50 ton tank overloads the engine and suspension and they break down. This forced the design of the KV-1S tank weighing 42.5 tons. Its engine power, layout, and hull robustness are insignificantly changed compared to the KV-1.
We cannot tell you if the suspension can take 100 tons of recoil, as there is no experience in using guns that cause such a load. A lack of characteristics for this design makes it impossible to determine if it is reasonable to install it into a tank.
GABTU Chief, Colonel-General Afonin
BTU 4th Department Chief, Engineer-Colonel Nevarskov."