"Requirements for the F-34 gun mantlet
- The front facing shield covering the gun port needs to be 52 mm thick if cast and 45 mm thick if rolled.
- The armouring of the cradle and recoil elements can be stamped or rolled and welded. The front cover needs to be removable. The thickness of the front cover needs to be 35 mm, the
vertical sidessides sloped at 20 degrees must be 30 mm thick, top and bottom at least 15 mm. - The design of the gun mantlet needs to reliably protect the crew from bullets and splash from all elevation angles from -5 to +30 degrees. The armour strips that prevent bullets and splash from entering must be at least 15 mm thick.
- In order to balance the system, a weight of at most 50 kg can be installed on the recoil guard. If a weight of more than 50 kg is required, a balancing mechanism must be added underneath the gun cradle.
Representative of the BTU Chief, Military Engineer 1st Class, Korobkov
Representative of the 3rd Department of the BTU, Military Engineer 1st Class, Afonin
January 18th, 1941."