Johnson M1941 Machinegun

There seem to be very few detailed or complete images available of this weapon.
The M1941 was designed by a Boston lawyer and Marine Corps Reserve Captain named Melvin Johnson Jr. His goal was to build a semi-automatic rifle that would outperform the M1 Garand that the Army had adopted. By late 1937 he had designed, built and successfully tested both a semi-automatic rifle and a prototype light machinegun. Each shared a significant number of physical characteristics and common parts, and both operated on the principle of short recoil with a rotating bolt.
The Johnson LMG was one of the few light machineguns to operate on recoil operation and was manufactured to a high standard. It was fed from a sharply-curved magazine on the left side of the receiver, but could be charger-loaded from the right, or even reloaded with single rounds one at a time. The rate of fire adjusted from 300 to 900 rounds per minute.
When firing, recoil forces along with the mass of the weapon's moving parts all travelled in a direct line with the shoulder of the gunner. While this in-line stock can be seen in today's M16 rifle, it was a novel idea at the time. Since recoil was directed back into the shoulder, muzzle rise was minimized. Due to this design, the sights had to be placed higher above the bore, giving the distinctive foresight look.
Although never officially adopted by the US Military, it saw service with mainly Marine Raider Units and Special Service Forces, where it appears to have been quite popular.