Shortround6
Major General
Problem is that the Germans had started using 30mm side and rear armor on the MK III and MK IV tanks in 1940. It varied a bit.
The light stuff was vulnerable but then it was vulnerable to the 12.7mm Soviet MG ammo too.
The 20mm Shvak cannon was actually a pretty poor hole puncher.
The 20mm didn't bring much to the table as a hole puncher which is not surprising considered that they just necked up the 12.7mm X 108mm machine gun case and cut off 9mm to get the overall length down to fit the mechanism. About the same space for the gun powder. A 20mm Shvak is delivering about 60% of the energy to armor plate as a 20mm Hispano near the muzzle and the Hispano doesn't fall off quite as much with range. If 20mm Hispano's won't do the job then the 20mm Shvak needs a lot of wishful thinking.
Explains why the Soviets went for 23mm gun. It had over 2 1/2 times the energy of the Shvak and about 56% times the energy of the Hispano while trying to blow a hole about 32% bigger (in area).
The 12.7mm machine gun actually delivered more energy per sq mm of hole area. A 20mm is trying to blow a hole about 2 1/2 times the area of the 12.7mm (again area). Increasing the energy of the projectile by 66% doesn't work.
Now getting the hits was also not easy. Perhaps a bit easier in some areas of Russia? fewer pesky telephone wires or trees next to the roads
Guns were much easier to hit with than rockets.
The light stuff was vulnerable but then it was vulnerable to the 12.7mm Soviet MG ammo too.
The 20mm Shvak cannon was actually a pretty poor hole puncher.
The 20mm didn't bring much to the table as a hole puncher which is not surprising considered that they just necked up the 12.7mm X 108mm machine gun case and cut off 9mm to get the overall length down to fit the mechanism. About the same space for the gun powder. A 20mm Shvak is delivering about 60% of the energy to armor plate as a 20mm Hispano near the muzzle and the Hispano doesn't fall off quite as much with range. If 20mm Hispano's won't do the job then the 20mm Shvak needs a lot of wishful thinking.
Explains why the Soviets went for 23mm gun. It had over 2 1/2 times the energy of the Shvak and about 56% times the energy of the Hispano while trying to blow a hole about 32% bigger (in area).
The 12.7mm machine gun actually delivered more energy per sq mm of hole area. A 20mm is trying to blow a hole about 2 1/2 times the area of the 12.7mm (again area). Increasing the energy of the projectile by 66% doesn't work.
Now getting the hits was also not easy. Perhaps a bit easier in some areas of Russia? fewer pesky telephone wires or trees next to the roads
Guns were much easier to hit with than rockets.