Project 423 was an ersatz SPG designed by the artillery chief of the Kirov factory, Lev Izrailyevich Gorlitskiy. The SPG consisted of a 76 mm regimental gun on a cruciform mount, surrounded by an armoured shield, similar to the one used on the T-26-6 (more commonly known as SU-26).
"August 5th, 1941
To the Chairman of the GAU UVNA
Senior Military Representative at the Kirov factory
Director of the Kirov factory
Report on the robustness trials of the automobile (ZIS-5) mounted 76 mm model 1927 regimental gun
Refer to letter #188 sent by the Kirov factory on August 2nd, 1941
Goal of the trials: robustness trials of the automobile SPG by means of firing with an increased power round. (Factory trials)
Trials by firing
The automobile SPG arrived at the ANIOP on August 2nd, 1941 at 20:30 along with ammunition. The SPG consists of a 76 mm model 1927 regimental gun on a special mount installed in a ZIS-5 truck.
The trials program was edited during the trials by the chief designer of department #4 of the Kirov factory, comrade Gorlitskiy.
Firing was done in three positions (see diagram).
In all positions, the SPG was tested by firing at an angle of 0 and 24 degrees. In each position, 10 shots were fired using an increased power round and or regular round with a wooden plug.
Inspection of the SPG before firing showed that at angles of elevation of 20 degrees or higher, the panoramic sight range from 15-00 to 45-00 is covered completely.
As a result of the robustness trials in the volume of 30 shots (28 were made while stationary, 2 while on the move), the following was recorded:
- The rear window of the driver's cabin was broken, despite being protected by a metal shutter. The front window cracked. The side windows were broken. The separator wall of the two crates in the left front section of the vehicle was broken. The covers of both crates flew off. The left door to the cabin was broken. Perpendicular beams that held the roof of the cabin were broken.
- The damage recorded was chiefly incurred by firing at a traverse angle of 315 degrees. Presumably, the same effect will occur at an angle of 45 degrees.
- It is necessary to reduce the traverse of the gun mount to protect the cabin from damage.
- When firing from standstill at a traverse angle of 180 degrees, the truck was shifted by 20-25 cm with every shot, despite the handbrake being engaged.
- When firing at a traverse angle of 270 degrees, the left wheel of the truck jumped up noticeably, but the vehicle did not shift. The same happened when firing at a traverse angle of 315 degrees.
- When firing at an elevation angle of 24 degrees, the recoil was short by 15-40 mm. The pressure in the recuperator was 24 atm.
Deputy Chief of the ANIOP, Military Engineer 1st Class Serebryakov
Chief of the 6th Department, Lieutenant Colonel Galkin
Experiment coordinator, Military Engineer 3rd Class Aksel"
Photos from newsreels by sirjones.