"Changes and simplifications of the hull and turret
On November 25th, 1941, the factory moved to a simplified hull. The mechanical cutting of the rabbets was simplified. The stamping of the lower rear plate (part 34.29.007) was also simplified. The full album of bluprints and technical requirements were sent out in the first few days of February.
According to the decree of the Committee of Defense the factory should have began building tanks with applique armour on the hulls and turrets by January 15th, 1942. In practice the first hull with applique armour was produced on February 25th, and the first turret on February 21st. In total there were 80 hulls and 109 turrets built with applique armour.
On February 13th, 1942, the Deputy People's Commissar of Tank Production comrade Goreglyad cancelled the applique armour.
On the thicker turret armour project, 4 samples were given to the factory. By March 1st 8 turrets with 75 mm thick walls were cast. These turrets are put into production.
In early February the factory performed experiments in extracting the gun from the turret through the turret ring. The results were successful and the factory was able to get rid of the opening in the rear (item 34.30.011). The turret is now more robust and reliable.
Starting with mid-February the hulls have been produced with a splash guard in the front that protects the turret from jamming. The splash guard is placed to cover the gap between the turret ring and hull roof.
Military representative of the BTU at factory #112, Military Engineer 2nd Class Gusak"