"Based on experiences of tanks fighting in cities and in mountains, GABTU requested that Artkom develop tank guns that can fire with elevation of up to 70 degrees. Therefore, tank guns based on the M-42 currently being tested should have depression to -6 degrees and elevation of up to 70 degrees. The recoil brake and return mechanism should be tested at maximum elevation.
Due to the high elevation, the recoil is allowed to be variable, and the recoil brake must be strengthened. An additional return mechanism mounted on top of the gun in the mantlet is allowed. In order to provide smooth braking, the recoil brake must be variable at various elevations.
If tank guns based on the M-42 are nearing completion and these changes will be difficult, it is necessary to begin designing new prototypes that satisfy the above requirements."
However, before testing a fancy new gun at high elevation, it's reasonable to try it with an old gun. Doing this revealed some problems.
"The T-80 tank design proposed by comrade Astrov, deputy chief engineer at the GAZ Molotov factory, is an interesting design, as it offers the possibility of shooting at enemy aircraft.
At the same time, the T-80 has a series of drawbacks, such as:
- The angle of elevation (65 degrees, 60 in the prototype) is not enough for quality AA fire, which requires an angle of elevation of at least 85 degrees.
- The rate of fire is 14-15 RPM, which is not enough for an AA gun.
- The sights are primitive and observation from the turret is limited, which is unacceptable for an AA gun.
- The recoil mechanisms do not operate in normal conditions, and a knocking is heard when the gun is returned at low elevations, requiring a new recoil brake and return mechanism combination.