T-70 Gun Choice

In the process of improving the combat performance of the T-60, the issue of re-armament came up. The two choices were the existing 45 mm tank gun and a newcomer, the more compact 37 mm ZiS-19. However, the 37 mm gun was at a severe disadvantage.

"To the chief of the artillery department of the GABTU BTU, Military Engineer 1st grade, comrade Nenarokov

In response to your letter #705118s from March 22nd, 1942, I reply that the NKV technical council lacks data on the factory #92 37 mm gun. Data has been requested.

Preliminarily, it can be said that that the 37 mm factory #92 gun uses a 0.7 kg shell with the muzzle velocity of 850 m/s. The existing 45 mm gun has a 1.41 kg shell, and the muzzle velocity of 760 m/s. We are also modernizing the 45 mm model 1937 gun to increase the muzzle velocity to 920 m/s. The modernization can be transferred over to the 45 mm tank gun.

Comparing the penetrations of the systems, we get the following table of theoretical armour thicknesses that can be penetrated at ranges of 200, 400, and 600 meters at an angle of 30 degrees from normal. The armour is non-cemented.

System	Range
	200	400	600	Muzzle velocity
37 mm	36	32	28	860
45 mm	41	38	36	760
45 mm modernized	56	52	49	920

From the point of view of production, most parts of the 45 mm tank gun are interchangeable with the 45 mm anti-tank gun, currently in mass production at two factories. It would be relatively easy to satisfy the requirement for such a gun. A 37 mm gun would have to be manufactured anew at one of the factories.

Currently, there is no free manufacturing power at any factory, and resolving this issue will be difficult. 

Considering the aforementioned, I consider it correct to select the 45 mm tank gun for use in the T-70 tank.  I will be able to provide additional reasoning when I receive the data from factory #92.

Chair of the NKV technical council, Professor, Doctor of Technical Sciences, E. Satel"

CAMD RF 38-11355-668