There were some rarely known weapons that saw action in the hands of Soviet soldiers and ordinary citizens against the Nazi invaders in 1941. For example, the designer Korovin, who worked at the Tula arms factory, rapidly developed and put into limited production a relatively simple SMG with a folding stock. This gun was never officially tested or approved – all specimens went from the workbenches of the factory straight into combat, carried by volunteers of the Tula arms factory regiment, fighting the Nazi invaders at the outskirts of the Tula city. Korovin managed to produce several hundreds of these weapons, chambered for the standard 7.62mm pistol ammunition. Once the front had stabilized and volunteer regiments were properly incorporated into the Red Army structure, these non-standard weapons were recalled from service and replaced by the standard issue rifles and PPSh-41. Only few of the Korovin SMGs survive to this day.
Korovin submachine gun is a simple blowback operated weapon, firing from open bolt in full automatic mode only. Most of its parts, except for barrel and bolt, were made from stamped steel and spot-welded together. Feed was from 35-round double stack, double feed curved box magazines, not compatible with PPSh-41 magazines. Korovin submachine gun was fitted with simple flip-up sights, marked for 100 and 200 meters, and an underfolding stock.