Suomi KP/-31 Submachine Gun — Finland’s Konepistooli

By Peter Suciu
Posted in #Guns #History
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Suomi KP/-31 Submachine Gun — Finland’s Konepistooli

December 5th, 2023

11 minute read

The Suomi KP/-31 submachine gun proved to be a pivotal Finnish firearm that inspired the Soviet PPSh-41, the most extensively produced submachine gun in World War II. Featuring a high-capacity drum magazine, selective-fire system and a quick-change barrel, the Suomi submachine gun was quite innovative for its time. In today’s article, Peter Suciu examines the development of the Finnish Army’s submachine gun and describes its lasting legacy.

suomi kp/-31 smg submachine gun finland army winter war continuation war
Lieutenant Eino Penttilä with his deputy team leaders of a patrol near Rukajärvi on September 8, 1942. The men carry the Suomi KP/-31 submachine gun. Image: SA-kuva

The Soviet Red Army’s Pistolét-pulemyót Shpágina-41, or “Shpagin’s machine-pistol-41” (PPSh-41) was the most-produced submachine gun of the Second World War, and even perhaps history, with about six million made in total. Though it is most well known for its service in use by the Red Army in World War II, it would go on to see service in countless wars — including in Korea and Vietnam.

It was often supplied to guerrilla forces that attempted to spread communism through force. [Ed. Note: Be sure to read our article Small Arms of the Viet Cong.]

finnish soldier in continuation war armed with 9mm suomi smg 71 round magazine vented barrel
The Suomi submachine gun was a rude surprise for the Soviet Red Army. The Model 1931 is shown in the hands of a Finnish soldier in the Aunus Isthmus region in August 1943. Image: SA-kuva

There are even reports that the weapon, chambered for the Soviet-designed 7.62x25mm Tokarev round, has seen limited use in the ongoing conflict in Ukraine. The Ukrainian Ministry of Defense had around 300,000 of the World War II-era weapons in storage and some have been pressed into service with second-line troops.

finland army soldier suomi sub machine gun 9mm continuation war
A soldier with a Suomi submachine gun in a defensive position during the Continuation War against the Soviet Union. Image: SA-kuva

That fact comes with some irony as the PPSh-41’s design was influenced by an SMG employed by another nation that Moscow invaded in the hope of widening its sphere of influence.

finland army patrol engages soviet troops near stalins canal
A Finnish patrol engages the enemy along Stalin’s canal. Officially the White Sea-Baltic Canal, it was built by the communists with forced labor, resulting in about 25,000 deaths. Image: SA-kuva

That firearm was the Suomi KP/-31 — sometimes listed as Model 1931 — a weapon that bears more than a passing resemblance to the firearm it would so greatly influence, notably the wooden stock and 71-round drum magazine. Though the PPSh-41 was noted for being a reliable weapon that earned the respect of those who carried it as well as those on the receiving end of it, the KP/-31 was also regarded by many as one of the most successful SMG designs of the Second World War.

Origins of an Iconic SMG

Finland, which had been ruled by Russia for more than a century, finally achieved independence at the end of the First World War. The February Revolution of 1917 brought down the centuries-old monarchy, followed by the October Revolution that resulted in Russia falling into civil war. This provided Finland with its opportunity for autonomy.

aimo lahti designer of suomi kp -39 smg
Aimo Lahti developed a number of small arms for the Finnish military forces including the KP/-31. This image was taken in 1940.

Determined to retain its independence, and with few in the way of allies, Finland began to develop a domestic arms industry. Leading the efforts was master armorer Aimo Lahti, who has been described as a “Finnish John Moses Browning.” He quickly began to design a new class of weapon, one that could provide infantry with sustained firepower in close combat situations.

Lahti was truly a visionary as the recently concluded First World War (then known as the “Great War”) had only seen the introduction of just a handful of SMGs — notably the German MP-18. Yet, he understood the promise it could bring in close-quarters combat.

commander in chief finnish defense forces major general lauri malmberg suomi submachine gun aimo lahti tikkakoski oy
Commander-in-Chief of the Finnish Defense Forces, Major General Lauri Malmberg, with the Suomi submachine gun designed by Aimo Lahti and manufactured by Tikkakoski Oy. Image: SA-kuva

It is entirely possible that Lahti may have been able to study an MP-18, but it is just as likely that he was able to examine another weapon that had arrived too late for the major conflict in Europe. That was the Thompson SMG, as a small number were known to have been used in the Baltic State Wars that were fought from 1917 to the mid-1920s. This could explain why Lahti’s design incorporated selective fire — with both semi- and fully-automatic fire. That feature was present with the Thompson, but missing from the MP-18.

The M-22 and KP/-26 Submachine Guns

Lahti developed his first SMG in 1922, a firearm that was simply dubbed the Suomi, although firearms historians now describe it as the M-22. It should be noted that though Lahti was quite the prolific designer, he wasn’t much for names — as Suomi simply means “Finnish” in the Finnish language!

finnish soldier sets up ambush for soviet union troops with suomi smg in continuation war
A Finnish soldier waits to ambush Soviet troops during the Continuation War. He is armed with the Suomi KP/-31 submachine gun. Image: SA-kuva

It isn’t known how many M-22s were produced, but it was arguably a prototype that led to the development of the KP/-26, which was produced at Lahti’s firm Konepistooli Oy. As with the M-22, the KP/-26 was produced in small numbers, but it was a far more refined weapon.

The KP/-26 was chambered for the unique 7.65mm Parabellum (7.65×21) cartridge due to the fact that it was the service pistol round of the Finnish Army. It was also equipped with a quick-change barrel and a recoil buffer that was designed to stop the rearward movement of the bolt by compressing air inside a chamber and — by altering the air escape port — could be adjusted to change the rate of fire.

finnish jaeger battalion 1 troops jp1 armed with suomi model 1931 submachine guns in continuation war
Finnish 1st Jaeger Battalion (Jääkäripataljoona) troops near the Mannerheim Line armed with Suomi model 1931 submachine guns. Image: SA-kuva

The KP/-26 also was fitted with a charging handle that ran beneath the bolt, which allowed a prone or stationary soldier to charge the weapon.

The KP/-31 Takes Shape

The Suomi KP/-26 was a fine weapon, but Lahti continued to improve his design. Along with assistance from Lieutenant Y. Koskinen, Lahti developed the KP/-31, which further refined the Finnish SMG.

finland soldiers battle against soviet untion poventsa fire and street fight
Poventsa fire and street fights in July 1942. Part of the Continuation War, this battle was fought inside modern-day Russia. The soldier is armed with a KP/-31. Image: SA-kuva

As with the KP/-26, it had a barrel inside a perforated cooling jacket/barrel shroud. Whereas the former weapon was fed from a curved magazine, the new design was fed from either a straight/stick box magazine or a drum magazine that could hold 71 rounds. It utilized a straight blowback action and also featured a quick-change barrel, which could allow for nearly unlimited sustained fire. It was an uncommon feature then and even now for an SMG.

finnish soldier drum magazine suoimi kp -31 smg submachine gun stick mag grenande continuation war winter snow
A Finnish soldier has a drum magazine in his Suomi KP/-31 submachine gun with stick box mags next to him in his prepared position. The photo was taken in the Ostrobothnia area. Image: SA-kuva

Notably, the KP/-31 was chambered for the 9x19mm Parabellum round that was developed for the P08 Luger pistol. This is the same cartridge used in the aforementioned MP-18 SMG. Arguably, it provided the SMG with a bit more stopping power. The KP/-31 had an effective range of 200 meters, and a rate of fire of up to 900 rounds per minute.

finland soldier in bunker with suomi kp:-31 smg ambush red army soviet union continuation war
In March, 1942, a Finnish soldier of the 8th Jaeger Battalion watches for enemy movement in a fortified observation post. He is armed with a KP/-31 using stick-type magazines. Image: SA-kuva

As the late Ian V. Hogg, noted firearms historian, described in his book “The Complete Machine-Gun — 1885 to the Present” (Phoebus Publishing Company, 1979), it was “an extremely well-made and reliable weapon which, for many years, was the standard by which other designs were judged. Somewhat heavier than most submachine guns, it compensated for this by being rather more accurate.”

Charged by pulling the handle straight back, a soldier could operate the KP/-31 like a carbine, using the right hand to change the magazine and charge the weapon while maintaining it at the ready with the left hand.

finland soldier sentry guard with 9mm smg suomi model 1931
A Finnish soldier waits for Red Army troops near the village of Uuksujärvi in August 1944. Image: SA-kuva

The Sumoi KP/-31 was upgraded towards the end of the Second World War with the addition of a muzzle brake that helped make it easier to control on fully automatic fire. KP/-31 submachine guns were manufactured by Tikkakoski Oy. 

Taking Notice of the Suomi Model 1931

Though the KP/-31 was adopted by the Finnish military, it was actually first employed in combat with the forces of Bolivia and Paraguay during the Chaco War (1932-35), which was fought by the two South American rivals for control of the Gran Chaco region. That largely forgotten conflict actually served as a test bed for new military platforms from aircraft to small arms, even before the Spanish Civil War.

finnish ski patrol soldiers kp -31 smg winter white camo clothing snow
Lieutenant von Blücher, the son of the German ambassador in Finland, prepares to lead a ski patrol in the Leningrad Oblast during March of 1942. His KP/-31 submachine gun is wrapped in white. Image: SA-kuva

A number of the KP/-31s were supplied to Bolivia, which had adopted the German P08 pistol, and some of those were almost certainly captured by Paraguayan forces — although Paraguay bought arms from any nation that would sell them. 

soldier armed with suomi kp -39 smg 9mm machine gun waiting to ambush soviet union troops
A battle-hardened bearded warrior, Suomi SMG at the ready, prepares for combat with Soviet Union troops during the Battle of Vuosalmi in July 1944. Image: SA-kuva

The Finnish SMG next saw use in Spain with both the Republican and Nationalist forces.

However, despite the fact that some Red Army “advisors” would have almost certainly seen and perhaps even handled the KP/-31 during the conflict in Spain, the weapon was used to devastating effect during the Winter War (1939-40) when the Soviet Union invaded Finland. The capabilities of the Suomi KP/-31 seemed to have taken the Red Army by surprise — as much as Finland’s tenacity and determination.

quick change barrel cleaning weapon maintenance field strip break down soldier military suomi model 1931 machine gun
During a break in the fighting, a Finnish soldier field strips and cleans his Suomi KP/-31 submachine gun. Image: SA-kuva

After seeing it in action, the weapon was noted to have a profound effect on Soviet authorities, who had been dismissive of SMGs. Almost immediately, the 71-round drum magazine was copied and adopted by the Soviets for the PPD-40, the forerunner of the PPSh-41.

soviet union equipment captured including ppd-40 smg drum magazines and tokarev pistol
Shown is the captured equipment seized from Soviet paratroopers killed in Orimattila, Finland. A pair of PPD-40 submachine guns with drum magazines are visible in the photo. Image: SA-kuva

U.S. authorities, who made note of the problems that the Red Army encountered in fighting Finland during the Winter War and the Continuation War, praised the KP/-31. A 1942 U.S. War Department report released during the Second World War also called out the key attributes of the “Suomi machine carbine” as it was described.

olavi alakulpi demonstrates smg elvis presley driver knight mannerheim cross
Lt. Olavi Alakulpi, Knight of the Mannerheim Cross, demonstrates how to use the KP/-31. After the war, Alakulpi emigrated to the U.S., joined the Army and fought in Korea. While a company commander in West Germany, Elvis Presley was assigned as his driver. Image: SA-kuva

“Something entirely different is required for warfare in the Finnish woods. Here the weapons must be located far forward and maximum fire power attained immediately. This demands an automatic weapon which is light and mobile. This weapon must be unusually well-balanced to ensure good aim under difficulties incident to forest fighting. The Suomi carbine is the weapon which fulfills all these requirements.”

finland army soldier demonstrates teaches shooting with suomi kp -31 smg submachine gun 9mm gun carbine
A soldier of Finland’s military forces demonstrates a Suomi KP/-31 SMG near Tuusula in 1943. Image: SA-kuva

The Suomi KP/-31 saw use with the Finnish military against the Soviet Union in the Winter War and the Continuation War and the brief fight against Nazi Germany during the Lapland War, while it was also employed by the Israel Haganah in the 1948 Arab-Israeli War. Finland produced a number for evaluation by Estonia before the Baltic State was annexed by the Soviet Union in June 1940, while it also provided a number to its Bulgarian allies during the Second World War. German paramilitary and police forces used the Suomi KP/-31 in limited numbers.

finnish army soldiers ready weapons guns firearms for battle skirmish attack ambush
Finnish soldiers of the Field Guard ready their firearms for combat in May 1944. The soldier closest to the camera seats a stick magazine in his KP/-31 SMG. Image: SA-kuva

The Soviet Union further employed captured KP/-31s during the war, while a clone was produced in Leningrad as the Karelo-Finskii KF-42, chambered in the 7.62x24mm Tokarev pistol round used with the PPSh-41.

finnish sniper on train roof with submachine gun
Finnish snipers armed with SAKO rifles were efficient in their work. Many carried an SMG for closer work. This sniper sits atop a train roof with his Suomi KP/-31 submachine gun in hand. Image: SA-kuva

In an interesting twist, one of the most famous users of the KP/-31 was Simo Häyhä, aka the White Death, one of Finland’s most noted snipers. On a few occasions, he was assigned to an assault squad, during which time he may have killed 200 of the 500+ Red Army soldiers he is credited with.

In Popular Culture

The Finnish KP/-31 hasn’t exactly been among the most popular weapons in popular culture. In fact, it has only been seen in a handful of films, with most being made during the Second World War by the Soviet Union. Its “Hollywood” debut only came in the 1979 film Cuba where it is seen used by guerilla forces. However, it is likely that it was actually a stand-in for the PPSh-41 as there is little evidence that any KP/-31s were used in the Cuban Revolution.

finnish soldier in defensive position with suomi kp -31 model 1931 smg sub machine gun ostrobothnia snow entrenched fortified
A soldier looks down the sights of his KP/-31 submachine gun on the front line in the Ostrobothnia region of Finland. Two additional drum magazines are at hand for fast reloading. Image: SA-kuva

Not surprisingly, the weapon appears in all three versions of the Finnish-made film The Unknown Soldier, which tells the story of Finnish soldiers during the Continuation War, when Finland attempted to regain the land lost in the Winter War. 


One of the biggest downsides of the KP/-31 was its high cost to produce, but that resulted in a rugged and reliable weapon. While fewer than 10,000 were reportedly produced, parts kits have shown up in the United States, and “dummy” non-firing models have been offered for sale.

[Be sure to read our article How to Legally Own a Machine Gun for additional information.]

These can still fetch upwards of $1,000 due to their rarity, while a Class III/NFA transferrable C&R KP/-31 was sold by Rock Island Auction (RIA) Company in September 2018, for $19,550 — excluding fees. It was in the mid-range of the pre-auction estimate. Quality and rarity like this will cost you!

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Peter Suciu

Peter Suciu

Peter Suciu is a Michigan-based freelance writer who regularly covers military history and hardware for The National Interest and FoxNews. He has collected military small arms and headgear since he was 12 years old. His most recent book A Gallery of Military Headdress was released last year and is available from here.

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