To the GABTU Chief, Lieutenant-General of the Tank Forces, comrade Fedorenko
On the issue of mounting the 107 mm ZiS-6 gun in the KV-3 tank
Attached is the project for the installation of a 107 mm ZiS-6 gun in the KV-3 tank, which has the following characteristics:
- Muzzle velocity: 800 m/s
- Recoil resistance: 20,000 kg
- Mass of the recoil components: 1600 kg
- Mass of the oscillating components with the mantlet: 2600 kg
- Recoil length: 640+40 mm
- Shell: single piece
- Breech: semi-automatic
- Coaxial machinegun: DT
- Vertical gun range: +20 to -5
- Maximum vertical gun range obtainable with recoil brake: +40 to -15
- Fume extraction with compressed air is possible
- Shell casing length: 625 mm
- HE round length: approximately 1200 mm
- Initial return mechanism pressure: 50 atmospheres
- Sight: TD
- Mantlet: same as in the KV type turrets
- The gun will be tested in the KV-2 turret
Factory #92 is finishing the design of the ZiS-6. Despite this late stage, some improvements noted by your engineers will be made. Some of your requested changes cannot be made, as they require approval by the factory (the frame and mantlet are fixed in our design).
The request from your engineers to use a two-piece shell goes against the decision of the party and government, which factory #92 will not allow. On our side, factory #92 did everything possible to ease the loading of a one piece shell, including making the gun as compact as possible.
In order to resolve the issue of two-piece loading, contact the appropriate authorities.
Factory director [signature]
Chief Engineer Grabin"