Suomi KP/-31
Oy Tikkakoski Ab · Submachine Gun · Discontinued · 1931
Also known as: Konepistooli m/31, KP/-31, Suomi M/31
Overview
The Suomi KP/-31 is a Finnish blowback-operated, open-bolt submachine gun designed by Aimo Lahti and introduced in 1931. Firing the 9x19mm Parabellum cartridge from a hollowed conical bolt with a fixed firing pin, it is renowned for its accuracy, reliability in extreme cold, and its iconic 71-round drum magazine. The KP/-31 earned a fearsome reputation in the hands of Finnish troops during the Winter War and Continuation War, and is widely regarded as one of the finest submachine guns of World War II.
Specifications
| Weight (empty) | 4600 g (162.3 oz) |
| Overall Length | 870 mm (34.25") |
| Barrel Length | 314 mm (12.36") |
| Action Type | Blowback |
| Firing Mechanism | Open Bolt |
| Trigger Type | Single Action |
| Magazine Capacity | 71 rounds |
| Magazine Type | Drum |
| Muzzle Velocity | 396 m/s (1299 fps) |
| Muzzle Energy | 584 J (431 ft·lbf) |
| Effective Range | 200 m (219 yd) |
| Maximum Range | 500 m (547 yd) |
| Rate of Fire | 825 rpm |
| Barrel Rifling | Right Hand |
| Frame Material | Steel |
| Barrel Material | Steel |
| Stock Material | Wood |
| Finish | Blued |
Calibers
- 9x19mm Parabellum · primary · 9mm NATO — also known as 9mm Luger, 9mm NATO, 9x19mm
Features
- Firing modes: Semi Automatic, Full Automatic
- Feed systems: Detachable Box Magazine, Drum Magazine
- Safety mechanisms: Manual Safety
- Features: Quick Change Barrel, Wooden Stock, Select Fire, High Capacity Drum
Service history
Operators
- Finnish Defence Forces · adopted 1931 · as Konepistooli m/31
- Swedish Armed Forces · adopted 1937 · as Kpist m/37
- Nazi Germany (Wehrmacht)
Conflicts
- Winter War (1939-1940)
- Continuation War (1941-1944)
- World War II (1939-1945)
- 1948 Arab-Israeli War (1948-1949)
Production
Estimated total produced: 80,000 · Production years: 1931-1953
Approximately 80,000 produced; manufactured primarily at the Tikkakoski facility. Roughly 3,000 examples were supplied to Nazi Germany.
Origin
Country of origin: Finland
Designer: Aimo Lahti
Discontinued: 1953
Notes
The Suomi's high-capacity drum magazine and quick-change barrel directly influenced later designs, including the Soviet PPD-40 and PPSh-41 drum magazines. The weapon remained in Finnish reserve service into the late 20th century.
Background
Finnish ski troops wielding the Suomi inflicted devastating close-range losses on Soviet columns during the Winter War, and the gun's 71-round drum so impressed Soviet commanders that it was directly copied for the PPD and PPSh-41 submachine guns.