Blyskawica submachine gun (Pistolet maszynowy Błyskawica in Polish language; "Błyskawica" means "Lightning") was developed and built by Polish resistance groups that fought Nazi Germany during the WW2. The gun was based on the British Sten, but with certain modifications in regard to the feed, trigger unit and shoulder stock. About 700 Blyskawica submachine guns were built in 1943-45 by underground workshops, run by Polish resistance groups.
The Blyskawica submachine gun is a simple blowback operated weapon which fires from open bolt, in full automatic mode only. Feed is from doublestack, single feed magazine copied from the British Sten, magazine housing is located below the gun. The manual safety is located inside the trigger guard, in front of the trigger. Gun is equipped with the bottom-folding shoulder stock, inspired by the German MP.40 submachine gun. Sights are fixed, with forward post and rear aperture.