Wednesday 17 December 2014

Sliding Breech for the D-25

Today, it is well known that the screw breech the D-25 inherited from the A-19 restricted the maximum rate of fire. This was also already known in 1943, when the IS-2 was still undergoing trials, and work on improvements began before the tank even hit the battlefield.

"I report on the condition of development of a sliding breech for the D-25 and D-2.

A meeting was held to discuss this issue on November 22nd, 1943, with the following attendees:
  1. Factory #9 director, comrade L.R. Gonor.
  2. Chief engineer of factory #9, comrade D.A. Rykkov.
  3. Deputy chief engineer, comrade A.N. Bulashev.
  4. Chief of the experimental design bureau, N.G. Kostryulin.
  5. Deputy chief technologist, comrade D.B. Kerner.
  6. From the NKV: Chief of the Experimental Designs Department, Major-General of the Artillery Engineering Branch, comrade A.A. Tolochkov.
  7. From the Artillery Committee of the GAU: Engineer-Lieutenant-Colonel comrade P.F. Solomonov.
  8. From UPVNA GAU: regional GAU engineer for factory #9, Engineer-Colonel, comrade A.N. Abramov.
This meeting discussed two types of sliding breech: vertical-falling and horizontal. A horizontal sliding breech was decided upon for the experimental prototype, opening to the left. 

Currently, corrections are being made to the working blueprints. They will be sent to the plant today. All other blueprints for a horizontal sliding breech will be finished and submitted by November 28th of this year.

The breech design is compatible with the D-2 without any modifications (the D-2 will only achieve quarter-automatic operation).

Regional engineer for factory #9, Engineer-Colonel Abramov"


  1. That was a good read.

    Do we have anything on the further fate of the sliding breach version of the D-25? Why had it not made it to the front?

    1. It had. D-25 guns received a horizontal sliding breech sometime in 1944, before the straight UFP modification.

    2. And thus increase the rate of fire by..?

  2. Which were the rate of fire of the original and improved versions of the IS2?