Wednesday 10 August 2022

Thicker Roof

"May 8th, 1943
Conclusions of the 16th Department of the GAU Artillery Committee

1. General part:

On April 27th, 1943, the Artillery Committee received a proposal from the Uralmash factory to transition from producing the roof of the 122 mm SU-122 SPG out of 20 mm thick high hardness armour to 30 mm thick medium hardness armour.

The Uralmash factory motivates this proposal with the fact that due to many cutouts and welds of various components the roof is overloaded and cracks appear, which have to be covered with 20 mm thick applique armour.

Uralmash prepared several blueprints:

  • front roof section (35-29-526-2)
  • right lower fender (35-29-083-1)
  • upper front plate (35-29-085-2)
  • hatch flap (35-29-437-1)
  • packing parts (35-29-532-1, 35-29-441-1, 35-29-442-1, 35-29-531-1)
  • assembly blueprints (35-29-131sb-1, 35-29-121sb-1)
    10 pages total.
2. Technical part:

The technical documentation presented by UVZ shows that changes to various parts of the casemate have to be changed, since the installation of the observation devices and hatch flaps change. These changes were approved by the Chief Technologist of the factory, which guarantees that mass production of the vehicles would be sufficiently supplied with tools and jigs.

The thickening of the roof to 30 mm will increase the weight of the SPG by no more than 100 kg, which will not have an impact on its mobility.

The armour resistance of the roof doesn't change, since the lower hardness is compensated by greater thickness.

3. 16th Department Concludes:
  1. Allow the Uralmash factory to produce the roof of the fighting compartment from medium hardness armour in accordance with the presented blueprints.
  2. Store these conclusions with the 12th Department of the Artillery Committee alongside the reference copy of the Artillery Committee journal for 1943.
  3. Send the conclusions to:
    1. Copy #1: Artillery Committee file #705s
    2. Copy #2: reference copy, to the 12th Department
    3. Copy #3: to the Uralmash factory
    4. Copy #4: GBTU Tank Directorate
    5. Copy #5: GBTU regional engineer at the Uralmash factory
Deputy Chair of the GAU Artillery Committee, Colonel Zhevanik
Assistant Chief of the 16th Department of the GAU Artillery Committee, Engineer-Major Solomonov"


  1. The tag is wrong, tag is for ISU-122. Which this is obviously not.