KV Gun Upgrades

"The following work is necessary to perform trials of KV tank armament and improvement of blueprints:

1. Install the F-34 gun instead of the F-32 gun into the KV-1 tank at factory #92 by March 1st, 1941.
   A commission composed of representatives from ChTZ, the Kirov factory, GABTU, and GAU must perform trials and approve blueprints by March 5th, 1941. Factory #92 received a KV tank with a 76 mm F-32 gun on February 2nd, 1941.
2. Install the 107 mm F-42 gun instead of the M-10 gun into the KV-2 tank by May 1st, 1941. Perform trials and work on blueprints, presenting them to the NKO no later than May 15th, 1941. Factory #92 received a KV tank with a large turret on January 29th.

Experimental Guns

"To the Deputy People's Commissar of Defense of the USSR, Marshal of the Soviet Union, comrade Kulik

July 23th, 1940

I report on the status of experimental work on tank and anti-tank armament specified in meeting minutes from June 16th, 1940

1. Working blueprints of a powerful 76 mm anti-tank gun based on the USV produced by factory #92 are complete and sent to the manufacturing plants, aside from blueprints for the balancing mechanism and the rear of the mount.
2. Working blueprints for a powerful 76 mm tank gun based on the F-34 were developed and sent to the manufacturing plants.

Experimental Tank Guns, 1940

RGVA 20-38-2908

Name	Mass	Practical rate of fire	Horizontal range	Vertical range	Shot range at max elevation	Muzzle velocity	Shell weight	Shell capability	Notes
76 mm tank gun F-34 in a T-34 tank	1030 kg	6-8 RPM	360 deg	-4 deg +30 deg	11 km	680 m/s	6.5 kg	Penetrates 60 mm at 400 meters. Penetrates 50 mm at 30 degrees at 850 meters.	Using shells from the 76 mm divisional gun. Due by December 1st.
76 mm gun for the KV-1	1200 kg	5-6 RPM	360 deg	-4 deg +25 deg	14 km	813 m/s	6.5 kg	Penetrates 70 mm at 30 degrees at 1000 meters.	Uses shells from the 76 mm AA gun. Due by September 1st, 1940
85 mm gun for the KV-1	1200 kg	5-6 RPM	360 deg	-4 deg +25 deg	14.5 km	800 m/s	9.2 kg	Estimated: penetrates 88 mm at 30 degrees at 1000 meters	Due by September 1st, 1940
107 mm gun for the KV with oscillating part from the M-60 corps gun	1500 kg	3 RPM	360 deg	-3 deg +15 deg	12 km	730 m/s	18.8 kg	Penetrates 100 mm at 30 degrees at 900 meters.	Due by November 1st, 1940

The penetration numbers for the F-34 look a bit weedy, but that's explained by the use of existing 76 mm shells instead of custom made ones.

The next gun is the F-27, a gun with 76 mm mod. 1931 AA gun ballistics. The gun was trialled on the T-28 and was meant to be a firepower boost for KV-1 tanks, until the war began and it was discovered that such a boost was no longer needed. In 1943, an attempt was made to use a gun with these ballistics on the T-34, but the appearance of the T-34-85 made that unnecessary.

The 85 mm gun is the F-30, and its trials in 1940 should put to rest any claims that the upgunning of Soviet tanks to 85 mm was caused by Tiger tanks. This gun was trialled in the T-28 and then in the T-220, but did not finish trials before the war began.

The last gun is the ZiS-6 that we all know and love. The gun was designed for the KV-3, 4, and 5 tanks, and trialled in a KV-2 turret. Later, it was proposed for use in the IS-2, but lost that contest to the D-25.