The Nordic heavyweight
Michael Heidler takes a look at the Lahti L-39 anti-tank rifle from Finland
The designer of the wellknown M/31 Suomi also created a huge anti-tank rifle. Michael Heidler has details of the Lahti L-39.
Finland was hardly affected by the devastation of World War I and its soldiers did not take part in the hostilities unless they had voluntarily joined the army of the Russian Tsar. Thus, there was a lack of experience with the new heavy tanks that appeared towards the end. It was not until the 1930s that the Finnish Army began to think about appropriate weapons to counter the new masters of the battlefield.
When Finland resisted Soviet demands to move the border in Karelia, at the end of 1939, the Red Army crossed the border in the early morning of 30 November 1939 to take the area by force. Despite numerous successful defensive actions in The Winter War, the Fins were unable to counter the Red Army tanks. On 13 March 1940 the war ended with the Moscow Peace Treaty. Finland had to cede large parts of Karelia, including Vyborg, the country’s second largest city at the time, and
other areas to the Soviet Union.
The military leadership quickly recognised the lack of anti-tank weapons in this war, but only two of their own Lahti L-39 anti-tank rifles and a few British Boys anti-tank rifles were available. As the L-39 proved to be a good weapon, it was proposed as the future standard weapon of the army after the end of the fighting.
Its creator was the well-known Finnish designer Aimo Johannes
Lahti who, at the time, worked for the state-owned rifle factory VKT (Valtion Kivääritehdas) and who, among other things, had already developed weapons such as the M/26 machine gun and the M/31 Suomi submachine gun before the war. When the army leadership approached him with the wish to create an antitank rifle, he was able to push through a 2cm calibre weapon. At first, the authorities believed that the muzzle velocity of this calibre was too low to penetrate armour, but Lahti disproved this in extensive tests in the summer of 1938. The series weapons were thus produced in calibre 20x138mmB, the same cartridge that was used in the Swiss Solothurn S 18-1000 anti-tank rifle. The B indicates a belted round which spaces on the belt rather than the shoulder, rim or mouth of the case.
Conflicts of competence in the Ministry of War, and the infantry inspector Major General Erik
Heinrichs’ indecisiveness, delayed the manufacturing decision until 6 September 1939. The new weapon got the official military designation 20mm Panssarintorjuntakiväääri 39 (20mm anti-tank rifle 39), with Lahti’s model designation L-39 also being retained.
To increase firepower, Lahti designed the L-39 as a semi-automatic weapon with magazine feed from the top. The gunner could fire a full 10 rounds in rapid succession at the enemy tank before a magazine change was necessary. Due to the magazine, the rear sight and front sight are not centrally located above the barrel axis, but are offset to the left. The recoil was enormous, and although the self-loading mechanism already reduced it, Lahti also fitted a muzzle brake and a padded leather recoil pad. The barrel received a wooden jacket with numerous cooling holes for air circulation. This allowed the rifle to be gripped with bare hands when changing position, even when the barrel was hot.
The L-39 was a gas operated weapon with the piston located beneath the barrel. The gas system was also equipped with a gas pressure regulator to ensure the function even with increasing contamination. The recoil spring was so stiff that it was impossible to cock the weapon with a traditional cocking handle. Instead, a rotating crank lever on the right side of the gun was used to pull the bolt back. However, the mode of operation was unusual for a semi-automatic weapon, because the weapon was not immediately ready to fire again after one shot was fired. The bolt carrier was always caught in its rear position and was only released by operating a special lever integrated in the pistol grip. After this manual release by the gunner, the recoil spring moved the bolt carrier together with the bolt forward, pushing a new cartridge from the magazine into the chamber and tensioning the firing pin spring. Now the gunner could release the shot by pulling the trigger. The intention of this procedure was to enable cooling of the open gun during breaks in fire. Experienced gunners could achieve fire rates of up to 15 rounds per minute including magazine change. The empty cartridge cases were ejected downwards. The large trigger guard protected the gunner’s hand from the spent hot brass.
At 100m, the penetration rate was about 30mm of armour steel and at 300m distance still 25mm. The newer Soviet T-34 or KW-1 tanks were, however, much better armoured. Only by careful defensive positioning and rapidly firing into weak area on these Soviet tanks was it possible to destroy them. The weapon was also used against bunkers and, now and then, even a lowflying Ilyushin Il-2 Shturmovik was shot down. Normal infantry projectiles could not do much damage to these heavily armoured battle planes. Distant targets could be engaged or at least disturbed by explosive and incendiary projectiles up to several kilometres. The burning of dry forests in which the enemy had taken up position was also popular in the hot summer.
Probably the biggest shortcoming of the L-39 was, without doubt, its weight. The Finnish soldiers christened it norsupyssy (elephant gun). In the Finnish wilderness, the monster, which was over 2m long with an empty weight of 42kg, had to be dragged over uneven ground. The filled magazine alone weighed almost 7kg. The weapon was equipped with an unusual dual bipod, with two sets of legs, one with spikes for use on hard ground and the other with skids for use on softer ground or snow. The skids also helped when being pulled like a sledge by humans or reindeer.
Production of the anti-tank rifle was pushed forward with great urgency. This was a good thing, as the so-called Continuation War with the Soviet Union began in June 1941. The first 10 pieces left the factory in Jyväskylä on April 10, 1940. In total, the Finnish Army ordered 1,852 pieces of the L-39 and 224 pieces of the fully automatic anti-aircraft model L-39/44. The latter was created by removing the bolt catch. However, the high fire rate strained the mechanics and led to problems.
A large number of Lahti anti-tank rifles survived the war. The official losses amounted to only 312 pieces, even though the heavy weapon often had to be abandoned during retreats. In the post-war years, these weapons remained in the army depots for a long time, until they were sold all over the world in the 1960s and the rest were scrapped. ■
Acknowledgement: Photos courtesy of James D. Julia/Morphy Auctions (USA), SA KUVA (Finland).