The M1941 Johnson Light Machine Gun was an American recoil-operated light machine gun designed in the late 1930s by Melvin Johnson. It shared the same operating principle and many parts with the M1941 Johnson rifle and the M1947 Johnson auto carbine.
The M1941 light machine gun was designed by a Boston lawyer and Captain in the Marine Corps Reserve named Melvin Johnson Jr. His goal was to build a semi-automatic rifle that would outperform the M1 the Army had adopted. By late 1937, he had designed, built, and successfully tested both a semi-automatic rifle and a prototype light machine gun. Each shared a significant number of physical characteristics and common parts, and both operated on the principle of short recoil with a rotating bolt.
Johnson's light machine gun was one of the few to operate on recoil operation and was manufactured to a high standard. It was fed from a curved, single-column magazine attached to the left side of the receiver; company brochures list a 25-round magazine as standard. Additionally, the weapon could be loaded by stripper clip at the ejection port, or by single rounds fed into the breech. The rate of fire was adjustable, from 200 to 600 rounds per minute. Two versions were built: the M1941 with a wooden stock and a metal bipod, and the M1944 with a tubular steel butt and a wooden monopod.
When firing, recoil forces along with the mass of the weapon's moving parts all traveled in a direct line with the shoulder of the gunner. While this in-line stock can be seen in the M16 rifle today, 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.
The weapon has many parallels with the German FG42. Both feed from the left side, and both fire from an open bolt while in automatic, and a closed bolt while in semi-auto. Both weapons were awkward to carry loaded, both with a side-mounted magazine, the Johnson had an especially lengthy single-column magazine, and this feature tended to unbalance the weapons. Despite these similarities, there is no evidence that either weapon had any effect on the design of the other. Both weapons attempted to solve similar problems, and adopted similar solutions.
Prototypes of semi-automatic rifles, 25-round magazine-fed, based on the Johnson LMG were also produced. The M1947 Johnson auto carbine is an example.