The 9×41 Lahti was a final development by Amio Lahti during the late 1950’s after he had already retired from the VKT (Valtion Kivääritehdas = State Rifle Factory). During 1943 there were serious issues between him and the VKT management. The Finnish Army Ordnance Department at that stage of the war was fully occupied delivering existing wartime orders and completing repairs on existing arms and it did not have any spare capacity to adopt a new cartridge/weapon, one that had not even been tested yet. What led to further unhappiness was the fact that Lahti sought private patents on his designs that the company felt he did on company time. After the Army rejected his AL-43 design, he looked at private companies outside existing military circles. During 1944 Lahti teamed up with companies linked to a Finnish industrialist Rafael Lönnstöm to produce prototypes of the AL-43, all being for the 9×35 Lahti, although the 7,62×35 was also being considered and some of the earlier prototypes were converted to the 7,62. Testing continued into 1944 and plans were made for official production, but the winding down of hostilities put a stop to the project.

The Allied Control Commission to manage the defeated Axis Powers arrived in Finland on the 22nd of September 1944 to observe Finnish compliance with the Moscow armistice, signed between Finland on one side and the Soviet Union and United Kingdom on the other side on 19 September 1944, ending the Continuation War (also known as Second Soviet-Finnish war, which was a conflict fought by Finland and Nazi Germany, against the Soviet Union (USSR) from 1941 to 1944, as a part of World War 2). The leader of the Allied Control Commission was Gen. Andrei Zhdanov who also controlled the demobilisation of the Finnish Army. Part of this required Lahti to hand over his blueprints and designs. Lahti handed over the details of the L-41 machine gun but somehow neglected to tell the Russians about his AL-43 designs. He was forced into retirement as part of the demobilisation which was the final nail in the coffin of his project. By the late 1950’s however, Lahti used his AL-43 designs for an assault rifle development, the L-51, although there isn’t any evidence that the design went past the concept stage, but he developed two new cartridges for this project; one was a 7,62mmx41 and the other being the 9mmx41 and ordered small quantities of cases from Lapua from surplus military orders left over after the war. Lahti is considered today to have been far ahead of his time in terms of the assault rifle/cartridge development. During 1951 the Finnish military had a look at his L-51 designs, but still saw the assault rifle concept as a passing fancy and this was in all probability the final nail in the coffin for the Lahti cartridges.