M1941 Johnson machine gun
The M1941 Johnson Light Machine Gun, also known as the Johnson and the Johnny gun, was an American recoil-operated light machine gun designed by Melvin Johnson in the late 1930s. It shared the same operating principle and many parts with his M1941 Johnson rifle and M1947 Johnson auto carbine.
Source: Wikipedia — M1941 Johnson machine gun (CC BY-SA 4.0)