Suomi KP/-31
submachine gun
The Suomi KP/-31 (Finnish: Suomi-konepistooli m/31, lit. 'machine pistol Suomi m/31') is a Finnish submachine gun that was mainly used during World War II. It is a descendant of the M-22 prototype and the KP/-26 production model, which was revealed to the public in 1925. It entered service in Finland in 1931, and remained in use until the 1980s.
The Suomi KP/-31 is regarded by many as one of the most successful submachine guns of World War II. It also had a profound effect on the conflict beyond Finland as the Soviet authorities, who had been dismissive of submachine guns, were persuaded of their fatal efficiency by the Finnish forces in the Winter War of 1939–1940. Though a relatively early design, the Suomi was a formidable weapon: highly controllable and with accuracy similar to that of the mass-produced PPSh-41 but at the cost of a significantly higher mass to absorb recoil, with a lower rate of fire and an equally large magazine capacity. Its major disadvantages were its higher weight, high maintenance requirements and high production cost, which led to the later introduction of the KP/-44, a close copy of the Soviet PPS-43 but accepting the existing magazines and drums for the KP/-31.
The M-22 and KP/-26 were made by Konepistooli Oy, founded by Master Armorer Aimo Lahti, Captain V. Korpela, Lieutenant Y. Koskinen and Lieutenant L. Boyer-Spoof. The Suomi KP/-31 was designed by Koskinen and Lahti.
History
The Suomi KP/-31 went into serial production in 1931 by Tikkakoski Oy which was owned by German arms dealer Willi Daugs and most of these weapons were bought by the Finnish Defence Forces. The Finnish Defence Forces were equipped with about 4000 Suomi KP/-31 submachine guns when the Winter War started. During the course of the war, the design was altered in February 1942 with the addition of a muzzle brake, which increased the submachine gun's overall length by 55 mm and weight by half a pound.
This brief starts where responsible research should: with the source description of “Suomi KP/-31” as submachine gun. Everything that follows is an evidence route, not borrowed authority.
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The subject matters to the general reference register because the source frames it as submachine gun. Its deeper value depends on whether names, dates, institutions and citations support that framing.
The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Aug 10, 2026. The linked authority identifier is Q753845. 1 of 1 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank. The first chronological checks are 1925, 1931, 1939 and 1940.
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This entry incorporates text from “Suomi KP/-31” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.