Aimo Johannes Lahti and the Lahti L-35 Pistol

Aimo Johannes Lahti was born on April 28, 1898, in the small Finnish town of Viiala. He became a pivotal figure in Finnish firearms design – specifically the Lahti L-35 Pistol. He left school at the age of fourteen. Initially, he found employment as a glass blower at the town’s glass works. Driven by a keen interest in firearms, he spent significant time in the workshop of a local gunsmith. There, he honed basic machining skills and became well-versed in gun making and firearms design.

He remained there until May 1918, when the Finnish Civil War began. This conflict was fought between “White Finland” and “Red Finland” (the Finnish Socialist Workers Republic). This ultimately contributed to Finland’s independence from Russia. It leveraged the power vacuum that existed after the First World War.

Lahti gained his initial military experience as a volunteer with the White Army. He fought against the Red Finland and Russian Bolshevik forces. After completing his initial military service, he rejoined the railways. However, later that year, he was conscripted to serve in the military again. This time, he served with the First Regiment on the Russian border at Rajajoki. He later served as part of King Frederic Charles’ Body Guard, with the rank of Under-Sergeant. Lahti’s military service concluded at the regimental small arms workshop at Kouvola.

Lahti then rejoined the State Railways as a conductor. During this time, he was involved with the Riihimäki Protection Corps. This military group formed to oppose the Red Guards. In June 1921, he was offered a prestigious post. He became Weapon Master with the Keski-Suomi Regiment in Hämeenlinna.

He was now free to pursue his interest in weapons manufacture. This led to his first submachine gun design in 1922 (Finnish Patent 9886). Despite a successful prototype demonstration, the Finnish military initially showed little interest. Undaunted, Lahti formed a company to manufacture the submachine gun in 7.65mm Parabellum. He did this with the financial backing of three fellow officers. They successfully sold 200 units to the Finnish military. Smaller quantities were also acquired by Poland and Sweden.

The Lahti L-35 pistol — one of Finland’s most significant service firearms. Image: collector’s example, circa 1940.

Development of the Lahti L-35 Pistol

Early Career and Collaborations

In 1924, Lahti was employed by the Finnish Defence Ministry. Here, in conjunction with Major Arvo Saloranta, he developed the LS/26 Light Machine Gun. This was a short-recoil operated weapon, featuring a 20-round magazine.

It was considered highly advanced for its era, blurring the lines between an assault rifle and a light machine gun. It proved accurate and reliable, even in harsh Finnish winter conditions. Lahti was then transferred to VKT (Valtion Kivääritehdas), the State Rifle Factory. Production of the LS/26 was undertaken there. Lahti later attributed initial performance issues with the LS/26 to unauthorised alterations. These were made by the factory manager, Major Arvo Saloranta. Lahti’s subsequent rectification of these problems likely did little to endear him to Saloranta.

In 1926, Arvo Saloranta made a proposal. As head of the armaments department of the Ministry of Defence, he suggested Finland should manufacture a domestic design pistol. He envisioned a domestic pistol equivalent to the Luger but simpler in design. Saloranta undertook the design himself.

Saloranta had previously designed a .22 caliber (top half) practice conversion for the M/23 (Luger). Saloranta’s pistol incorporated a vertically displaced lock, an idea borrowed from the Danish Bergman 1910 pistol. Interestingly, the bolt and locking system bear strong similarities in both the Lahti L-35 Pistol and Saloranta’s design.

This raises questions: Was there initial design collaboration with Lahti? Or did Lahti later incorporate features from Saloranta’s design into his own L-35 pistol? Saloranta then assumed directorship of Valtion Kivääritehdas (the State Rifle Factory). Saloranta’s pistol prototype was manufactured at the Weapons School. It reportedly functioned satisfactorily, though only one prototype is known to exist.

The Suomi Submachine Gun

While working at VKT, Lahti received a new appointment. He became Chief of the newly established “Office of Light Weapons Construction.” During this period, he supervised the production of his modified submachine gun, the M/31. This weapon, better known as the “Suomi,” was chambered in 9x19mm Parabellum.

These were supplied to the Finnish Army and officially adopted in 1931. Approximately 80,000 M/31 ‘Suomi’ submachine guns were produced. Tikkakoski, the state metalwork factory, manufactured them between 1932 and 1944.

The Suomi was renowned for its excellent quality and reliability. It played a crucial role in the “Winter War” following the Soviet invasion of Finland on November 30, 1939. After four months of conflict, the Russians stated a willingness to negotiate a peace treaty. However, they reorganised and renewed their offensive in February 1940, initiating what became known as the “Continuation War.” In these conflicts, the densely wooded terrain proved highly advantageous for the submachine gun. As a primary infantry weapon, it led to very heavy Russian losses against the Finns.

The Genesis of the Lahti L-35 Pistol

From 1928 to 1932, Lahti worked on his semi-automatic pistol design. This is probably the weapon he is best known for outside Finland. The official service handgun at the time was the Luger Parabellum, supplied in 7.65mm caliber.

Germany was limited to producing handguns up to .30 caliber. This was due to the restrictions of the Treaty of Versailles. DWM supplied 5,000 of these pistols (designated the M/23 in Finland) between 1923 and 1935.

As these pistols returned for servicing at Tikkakoski, they were often re-barrelled to 9x19mm. Some also received longer (120mm) barrels. It is widely believed that the Luger did not perform optimally in Finnish winters. This was due to extreme low temperatures – down to −40∘C!

Of course, such conditions would reduce propellant impulse. This was a critical factor given the Luger’s reliance on full-power loads for proper function. This environmental challenge likely influenced Lahti’s design. He decided to incorporate a bolt accelerator, a feature also present in the LS/26. High-speed photography reveals the projectile exits the barrel well before the Lahti’s bolt begins to unlock. This added rearward acceleration significantly aided reliability in frigid conditions. The M/23 Parabellum continued in service during this period as L/35 pistols were manufactured and issued.

“The L-35 was not simply a copy of any existing design — it was a thoroughly Finnish solution to a thoroughly Finnish problem: how to make a pistol that would function reliably at minus 40 degrees.”

Design and Features of the Lahti L-35 Pistol

The Lahti L-35 Pistol is very similar in appearance to the Luger, as was Arvo Saloranta’s competing design. The 96mm barrel Luger weighs 890 grams unloaded. In contrast, the L-35 weighs 1245 grams unloaded with a 117.5mm barrel, making it a noticeably heavy pistol to use.

Its weight and balance, combined with its long sight radius, make it a very accurate pistol. It performs well on the range. Field stripping the Lahti pistol is remarkably easy. It follows a similar procedure to both the Luger and P38 pistols. After removing the magazine and verifying the chamber is clear, the barrel is pressed against a hard surface.

Field stripping the Lahti pistol is remarkably easy.

The takedown lever above the trigger is rotated downwards. This allows the receiver assembly to slide forward off the grip frame. The L-35 features a hollow rectangular receiver housing a rectangular cross-section bolt. These components can now be withdrawn from the rear of the receiver.

An inverted U-shaped locking block fits around the bolt. The top of this ‘U’ slots into a recess across the top of the bolt. Its sides engage with recesses inside the receiver.

Upon recoiling approximately 6mm, the locking block is cammed upwards by inclined surfaces within the frame. The bolt’s rearward momentum is further increased by the accelerator lever. This lever is positioned behind the barrel and opposite the ejection port. This lever pivots to strike the bolt face. Driven backward, the bolt rides over and cocks the internal hammer in the usual fashion.

Upon returning to battery, a fresh round is stripped from the magazine and chambered. If the magazine is empty, an internal hold-open latch retains the bolt in the open position. A slight retraction of the bolt releases it. Reassembly is the reverse of disassembly. When replacing the locking block, the arrow on the underside must point forward. Crucially, it is possible to reassemble the pistol without the locking block. This could lead to disastrous consequences if fired.

Production Variations and Markings

Several modifications were introduced during the L-35’s production run. Early models featured a loaded chamber indicator and a lock retaining spring housing in front of the receiver bulge. The receiver itself also had cutaway sides.

The second receiver type omitted the lock retaining spring and housing. The third receiver further eliminated the cutaway sides. It also dropped the curve at the rear of the chamber indicator.

The fourth and final modification was exclusively sold on the civilian market. In these models, the loaded chamber indicator was also removed. Early production pistols were intended for military use but failed army inspection. They were marked with a “V” prefix to their serial numbers and subsequently sold to civilians.

Post-war, remaining parts were assembled with new receivers. These were manufactured by Valmet (marked ‘Valmet’) and Vammaskoski (unmarked) and then sold commercially. These later guns lack the stock lug at the bottom of the grip frame. They also do not carry the “V” prefix. In total, approximately 9,100 Lahti L-35 Pistols were manufactured. They were produced for both the Finnish armed forces and civilian sale.

Handling and Accessories

The Lahti L-35 pistol features an angled, Luger-style grip and points naturally. However, its safety catch, located at the top right of the grip, can be somewhat awkward to manipulate.

A common criticism of both Finnish and Swedish Lahti pistols is the ability to engage the safety when the hammer is at half-cock. This is possible thanks to a dedicated half-cock notch. The author notes having owned and shot Lahtis for years. He only discovered this feature later, questioning its practical utility.

The sights are generally considered superior to those found on most military handguns. The foresight is also drift-adjustable for windage. The large angled lugs on the rear of the bolt make it easy to retract. This is true even with gloved hands. The trigger pull on the author’s L-35 pistol is described as crisp. It breaks at approximately 4.5 lbs with minimal over-travel.

Finnish service pistols were supplied with molded leather holsters. They featured a protective leather cover, secured by a short strap and buckle. These holsters also accommodated a cleaning rod, a spare magazine, and a combined magazine loading tool/screwdriver. The holster included rear loops for attaching a wooden stock, similar to an Artillery Luger stock.

Wooden stocks were indeed made for both Finnish and Swedish pistols. Additionally, a Finnish wooden holster-stock, reminiscent of the Mauser C96 ‘Broomhandle’ stock, also existed. The pistol was carried within this stock. It attached to the grip base via a curved steel mounting lug, similar to the Luger.

A lever on the left side engaged a series of stops. This locked the stock securely onto the grip. All wartime pistols featured a stock mounting lug. Despite this, the Finnish wooden holster-stock was apparently never officially adopted. The L/35 stock was notably not interchangeable with the Luger stock. Many authorities suggest these stocks are rare and were not widely issued. However, estimates of their production numbers vary considerably.

Later Life and Legacy of Aimo Lahti

In 1945, a group of Finnish officers hid caches of weapons at various sites around the country. This happened after the conclusion of the Continuation War against Russia. These caches were intended for use should Russia invade Finland again.

Finland was technically aligned with Germany during WWII due to their conflict with Russia. Consequently, Finland found itself occupied by the Allies at the war’s end. The weapons cache plot was subsequently leaked to the Allied Control Commission. In Finland, this commission was composed almost entirely of Soviet officers (15 British and 200 Soviet).

An investigation was promptly launched. As a result, Lahti was accused of concealing the whereabouts of 30 prototype assault rifles. He had been developing these. The investigation’s outcome barred Lahti from working at the Arms Ministry. It also prevented him from further weapons design.

He was placed under house arrest and prohibited from foreign travel. The prior death of his only son compounded his personal tragedies. His son, a fighter pilot, was killed in action against the Russians. He was ultimately pensioned off with the equivalent of a Finnish Army Major General’s pension. Lahti’s health declined, and he passed away on April 19, 1970.

Throughout his lifetime, Lahti designed the Suomi submachine gun and the L/35 pistol. He also designed assault rifles, anti-aircraft cannons, an anti-tank rifle, and light machine guns. In general, he made significant contributions to small arms design. With the possible exception of J.M. Browning, few other small-arms designers have contributed so significantly. Their contributions were vital to their country’s defence.

Civilian Sales and Swedish Adoption

The author’s L-35, serial number falls just outside the Finnish Army contract range (numbers 1105-6731). All pistols within this range featured loaded chamber indicators. It lacks the ‘Suomen Armeija’ (Finnish Army) acceptance mark. This is because military production ceased with the signing of the armistice. Pistols surplus to the initial military order (up to approximately serial number 6800) were subsequently sold. They were released onto the civilian market. Pistols with serial numbers from 6800 up to 9100 were assembled from existing parts. Some incorporated new receivers manufactured by Valmet (marked ‘Valmet’) or Vammaskoski (unmarked). These were also sold commercially.

The Lahti was adopted by Sweden in 1940 as the m/40. It was intended to replace the m/39 (Walther HP/P38). However, Germany was unable to fulfill the m/39 contract. This was due to the outbreak of WWII and overwhelming domestic demand for the P.38.

Collector’s Notes

The author’s personal L/35 has a serial number just beyond the Finnish Army contract range (1105–6731). It features the loaded chamber indicator but lacks the Soumen Armeija army acceptance mark. These later civilian pistols were built from surplus parts and new receivers post-armistice.

In 1940, Sweden adopted the Lahti as the m/40 to replace the m/39 (Walther HP / P38) after Germany was unable to fulfill contract deliveries due to WWII demands.