Suomi KP/-31
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The Suomi KP/-31 (Finnish: Suomi-konepistooli m/31 or "Finland-submachine gun mod. 1931") is a Finnish submachine gun that was mainly used during World War II. It entered service in Finland in 1931, and remained in use until the 1980s. It was designed by Aimo Lahti in the late 1920s.
The Suomi m/31 were used very effectively by Finnish forces in the Winter War of 1939-1940. It was a precise weapon, but very heavy to absorb recoil, with a lower rate of fire and a magazine capacity equal to that of the Russian PPsh-41 submachine gun (71-round drum).
Its caliber was 9 mm Parabellum, rate of fire of 750 to 900 shots per minute, it could use box magazines of 20, 36 or 50 rounds; or drum of 40 or 71 rounds.