During 1943 the Finnish authorities began showing a passing interest in an assault rifle/SMG concept like the 7.92 Kurz. They however did not have either the time nor the inclination to start the development of a whole new assault rifle/cartridge concept smack bang in the middle of a world war when they already had limited resources and were trying to keep up with the war demand. Finnish arms designed Amio Lahti saw the potential of a lightweight SMG concept and started his own development based on shortened 6.5×55 SE cases. This private venture, while in the employ of the VKT (Valtion Kivääritehdas = State Rifle Factory), lead to some serious personality clashes with management and he was accused of using company time and resources to further his own agenda. Ultimately his concept rifle, the light machinegun m/AL-43 was not adopted by the military, being rejected by Weapons-HQ of the Finnish Army HQ Commander Major General V. Svanström. Lahti was not however going to give up on his dream, and he started looking for outside funding of his project. The initial AL-43 was developed for the 9×35 Lahti cartridge, which was the first of his cartridge designs, the 7,62mm Lahti being developed afterwards.

Lahti also used a lot of his own resources in the development of these cartridges and ordered the cases from VPT (Valtion Patruunatehdas = State Cartridge Factory) from surplus brass from an earlier Swedish Military order during 1941. Therefore, all Lahti cartridges utilise the VPT 41 headstamp. 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 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. This very short sightedness was revealed when just a few short years later in 1956-57 the Finnish Military, in a 180 degree about face, adopted the 7.62×39 AK-47 as its official military cartridge.