It’s tough being the little guy on the block, especially when the guy picking on you looks like Drago from Rocky IV. Finland experienced a similar scenario in 1939 when the Soviet Union—partnering up with our favorite bad guys, the Nazis—faked an attack on one of their own villages to give them an excuse to invade their smaller neighbor to the west. The Soviets came at the Finns with an army of 19 divisions; the Finns could field only nine. But Finland also had something the Soviets didn’t: the Suomi KP/-31.

Weird Gun Wednesday: The Suomi KP/-31
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Where you’ve seen it:

Go figure, most films showcasing this chunky submachine gun are Finnish in origin, and pretty obscure as a result. The film The Winter War (right), shows the Suomi in use several times, if you’re willing to read some subtitles.


The Finns didn’t have the odds in their favor. They were forced to defend an 800-mile border against three times the infantry, 30 times the aircraft, and 100 times the armor of their forces. Fortunately, they had a few things going for them the Russians didn’t. First, Stalin’s Great Purge of 1937 had eliminated over 30,000 officers from the Red Army, leaving his forces with inexperienced and inefficient leadership. This didn’t help the Soviet troops feel particularly enthusiastic about fighting, either. Second, the Russian forces had no submachine gun in their arsenal. Mainline troops were equipped with the Mosin Nagant rifle, and for those who might own one or two, you know just how handy they’d be in close-quarters fighting: You’d be better served using them as a club. In contrast, the Finns had the automatic Suomi KP/-31, designed by Aimo Lahti in 1925, issued two to each squad. This proved to be an overwhelming advantage in firepower, the Suomi capable of dumping 9mm Luger rounds from a 71-round drum magazine. Though Finland eventually lost the war (it was hard to beat the Russian numbers), they blackened the eye of the mighty Russian army and left a lasting impression on the Soviets. So much so, in fact, the Red Army followed the design of the Suomi to develop their own close-quarters “burp” gun that saw extensive use in WWII—the PPSh-41.

The design:

The Suomi functioned on a straight blowback action, firing 900 rounds per minute. Parts were milled, making the Suomi of higher quality and higher cost than its stamped-steel protégé, the PPSh-41. A muzzle brake was added midway through the Winter War to help with the Suomi’s muzzle rise, but Lahti thought it made the gun less reliable and reduced muzzle velocity (the latter is patently false). So troubled that the army would adopt this addition to his design, Lahti attempted to have its designer court-martialed.

The cartridge: