Mors wz.39 submachine gun (Pistolet maszynowy Mors wz.39 in Polish language) was developed by Polish small arms designers Piotr Wilniewczyc and Jan Skrzypinski between 1937 and 1939. After extensive trials against the German-made Erma EMP-35 submachine gun, the Mors was officially adopted for Polish service in 1939 and production was ordered to the Fabryka Karabinów rifle factory. Only 36 Mors submachine guns were built before German army attacked the Poland in September of 1939, and all but two or three were lost in combat or destroyed by Polish soldiers to avoid possibility of the guns being captured by Germans. production of the Mors submachine guns was ceased shortly before German occupation of the factory, and all manufacturing plans were either destroyed or smuggled out of the country, out of the Nazi's reach. Because of the overly complex design, which was quite expensive to manufacture, production of the Mors submachine guns was never resumed after the war.
Mors wz.39 submachine gun is a simple blowback weapon which fires from open bolt. It can fire in single shots and full automatic thanks to two triggers (rear trigger provides single shots, front trigger provides full-automatic fire). Safety is provided by L-shaped cut at the end of the cocking handle slot, which is used to lock the bolt in the rear (cocked) position by putting the bolt handle into this cut. The bolt return spring is located inside the closed tubular guide, which, along with the cavity in the bolt, forms the pneumatic buffer. This buffer is used to reduce the rate of fire and improve accuracy of the gun when firing in full automatic mode. The barrel is enclosed inside the perforated barrel jacket and can be easily removed for maintenance or inspection (barrel lock is located in front of the magazine housing, on the right side of the gun). feed is from detachable box magazines with 25-round capacity, inserted from below the gun. Mors wz.39 submachine gun is fitted with wooden stock with semi-pistol grip and an additional forward vertical grip. This forward grip also hosts a telescoped (retractable) monopod which can be used to steady the gun when firing in prone position. The tangent type rear sight is adjustable for range between 50 and 600 meters.