The Russians updated their Model 1937 45mm anti-tank gun by lengthening the barrel from 46 to 66 calibres.   The breech block was strengthened and disc wheels replaced the earlier wire wheels.   Armour penetration increased by some 50% to 55mm at 1000m, 95mm at 300m.   As the Model 1942 the new gun gradually replaced the earlier 45mm guns and it remained in service long after the war.