Born into an affluent Boston, Massachusetts, family, he was commissioned into the Marine Corps Reserve in 1933 as a Second Lieutenant and completed Harvard Law School in 1934.
He also designed the Johnson Light Machine Gun, derived from the M1941 rifle, which was used in limited numbers during World War II and the M1947 Johnson auto carbine, also derived from the M1941 rifle and M1941 light machine gun.
Throughout the war, Johnson put up a lot of effort to promote his machine gun and rifle.
[2] Johnson also worked to improve the M1 Carbine eventually developing the 5.7mm MMJ (commonly known as .22 Spitfire) cartridge, unsuccessfully submitting it to the U.S.
In 1963, he then started Johnson Arms, Inc. to make, sell, convert, and promote M1 Carbines using his 5.7mm MMJ cartridge.