This ability, in a weapon that should be purely anti tank, should not be so lethal.
A good improvement would be to add a delay or animation before the first shot, in order to make it more "readable", similar to the AP ammo load on the HMG.
ZiS-3 is a field gun, not dedicated anti tank gun.
Its as much light artillery as it is anti tank gun and it was used extensively in both its roles, its not relics fantasy, its probably most historical portrayal of usage of unit we have in CoH2.
45mm and 57mm were soviet dedicated ATGs in WW2.