The Suomi KP/-31 was a sub-machine gun (SMG) of Finnish design used during World War II. It went into serial production in 1931 by Tikkakoski Oy and most of these weapons were bought by the Finnish Defence Forces. The Finnish Defense Forces were equipped with about 4000 Suomi KP/-31 sub-machine guns when the Winter War started
Technical Data Weight 4.6 kg (10.14 lb) Length 870 mm (34.3 in) 925 mm (36.4 in) (SJR) 740 mm (29.1 in) (bunker version) Barrel length 314 mm (12.4 in) Cartridge 9×19mm Parabellum Action Straight Blow-back Rate of fire 750–900 rounds/min Muzzle velocity 396 m/s (1,299 ft/s) Effective firing range 200m Feed system 20-, 36- or 50-round box, 40- or 71-round drum. Also modified German MP 38 u. 40 32-round box magazine Sights Front blade, rear notch