The Suomi KP/-31 (Suomi Konepistooli 31, or "Finland machine pistol 31") was a submachine gun used by Finland in World War II, and exported in small numbers to several other nations.
It was designed by Aimo Lahti from 1921 to 1931, produced from 1931 to 1953, and remained in service until 1998. The weapon is most commonly pictured with a drum magazine, which held 71 rounds of 9x19mm ammunition, but numerous other magazines were also used: a 20-round box, a highly unsuccessful 40-round drum, a 50-round quadruple-stack "Coffin" box, and post-WW2, a highly reliable Swedish 36-round box. The 71-round drum magazine inspired the very similar magazine of the Soviet PPSh-41.
