F.16 Op.2154 D.4"Top Secret
To the People's Commissar of Armament of the USSR, comrade D.F. Ustinov
On your orders, we report on the issue of replacing the D-25 gun in the IS tank with the D-10T.
- Due to the higher rate of fire of the D-10 compared to the D-25, chiefly due to the single piece ammunition, it is reasonable to make this change, but only if an armour piercing shell is developed equivalent in penetration to the D-25's shell.
- No such shell is being produced at this time.
- We consider it necessary to preserve the D-25 gun in the IS-2 heavy tank. The latest trials at the ANIOP show a rate of fire of 4-6 RPM, this is a good result.
- The factory is wrapping up preparations for D-10S production in August-September of 1944.
- All armament production can be moved to produce the D-10T instead of the D-25 in October-November.
- 150 D-10T guns can be produced in October, 250 in November.
- To achieve this, factory #9 requires 4 600x6000 roughing lathes and two #6 milling machines.
- Production of D-25S guns should then be transferred to factory #75 or #221 in October.
August 8th, 1944"