Thursday 19 September 2013

D-30 Gun for the IS-6

In 1944-1945, Soviet heavy tank industry was at its peak. A very interesting vehicle was being developed, the IS-6. Unlike its "predecessors" IS-3 and IS-4, (IS series indexing was not at all sequential), it did not just get a D-25T, but a more advanced gun, the D-30:

CAMD RF 81-12038-681

"On the question of experimental works at factory #9 for the 4th quarter

In addition to the experimental works at factory #9 that I have wrote about in quarterly reports, the following were completed in the 4th quarter:

1. 122 mm "D-30" tank gun with ballistics from the "D-25" tank gun.

Factory #9 completed experiments on the prototype tank gun (under its own initiative), which consists of:

  1. D-25's monobloc;
  2. D-10's breech and gas block;
  3. Balancing mechanism with two springs;
  4. Lengthened D-25 mount;
  5. Fume extractor mechanism.
The experimental D-30 system was tested by firing 30 special strengthened shells from a special stand.

Before shooting, markings were placed on the D-30. The gun fired 30 shells successfully. After shooting, the markings were not deformed. All mechanisms of the gun perform satisfactorily. The full report on the D-30 test was sent to the GAU Artkom indexed #1595/42s on December 5th, 1944 by factory #9. 

In December, after the tests, the gun was sent to factory #100 for installation in the IS-6 tank and continuation of trials."

The D-25 was considered powerful enough for years to come, and, as such, its firepower was not increased. However, the rate of fire was increased in two ways. One is the improved breech, which makes loading easier. That's not that interesting, at least not as interesting as the fume extractor. Existing IS-2 tanks could already fire fast enough that ventilation of the crew compartment could not keep up. The fume extractor expelled the fumes from the burning gunpowder from the front of the barrel, so they could not rush back when the breech was open after a shot, allowing the tankers to fire much faster without succumbing to CO poisoning. 


  1. Interesting. Did these strengthened shells have better penetration than regular ammunition, or was this just a test to see if the gun could fire?

    1. The strengthened shells used for testing guns have lots more propellant in them, so they do have more penetration. However, the whole point of them is that they put unacceptable wear on the gun. That's why they only fired 30 instead of hundreds.

      This is what happens when the gun isn't up to par:

    2. Oh, so just a test load to test the limits of the gun?

    3. Yes. Destructive testing is the best kind of testing :)

    4. Every single pic in your link is broken o.o

    5. Yes, Yuri Pasholok's picture hosting went tits up. I saved some of his scans, but a ton of them are gone, hopefully not forever.

  2. Way back cannon-makers were AFAIK actually obliged to *sit* on their products during the initial "proof shots" - this practice was apparently adopted after James II of Scotland was killed by a bursting gun in 1460.
    Talk about incentives. :/