Friday, 2 January 2015

End of the ZiS-25

In 1942, many officials in the Red Army did not have such a good impression of the KV tank. It was heavy, it was expensive, and ultimately, it brought the same 76 mm gun to the battlefield that the T-34 could. One attempt to improve the value of a KV tank was undertaken in 1942 with the ZiS-25 gun, but some problems arose.

"Conclusions on the 85 mm KV tank project

The blueprints of an 85 mm gun provided by factory #92 include only general blueprints of the gun and a specification of the parts that are different from the ZiS-5.

Advantages of this project include:
  1. Mass producing this gun will cause no problems, as many parts are the same as the ZiS-5.
  2. The muzzle velocity is increased by 72 m/s compared to the ZiS-5, and the mass of the shell is increased by 3 kg, increasing the penetration by 30 mm at a range of 1000 meters.
  3. There is already ammunition being produced for this gun.
Drawbacks include:
  1. The factory documents lack any kind of data on the rate of fire or ammunition capacity. Since the one piece shell of the AA gun is 985 mm long, or 336 mm longer than the ZiS-5 shell, it can be assumed that the practical rate of fire of the gun will be 1-2 rounds per minute. The shell length will not only negatively impact the rate of fire, but will reduce the amount of ammunition carried below acceptable levels.
  2. Tank units will have a new type of shell, which will cause difficulty with supplies.
The issue of how reasonable it is to produce this experimental gun was already decided. A letter was sent to the Commissar of Armament (comrade Ustinov) on October 27th, with a request to let factory #92 produce a prototype. 

I think it is necessary to add a condition that the gun provide a rate of fire of at least 5 RPM, since otherwise, there will be no advantage in firepower compared to a ZiS-5 gun.

Engineer-Major Afanasenkov"

I don't know if the gun was ever made or if it achieved the needed rate of fire, but it was not meant to be. The S-31 came to displace this gun soon, in turn being beaten by the D-5.


  1. Was the practical rof so low because of the KVs smal turret? What do you think?

    1. Yes, the shell was too long. The heavier, but two piece, 122 mm U-11 achieved a higher rate of fire.

      Keep in mind that this is just an estimate, so maybe the real ROF would have been higher than 1-2.