When the USMC adopted the M1 Garand in 1942, they decided they would like to have a new semiautomatic training rifle in .22 rimfire to go along with it. Eugene Reising, working for Harrington & Richardson, promptly produced a semiauto .22 LR version of his military submachine gun to fulfill that role, designated the Model 65. This rifle had a stock and barrel sized to duplicate the handling of the M1, and a nice aperture sight as well. By 1945, between 6,000 and 10,000 had been sold to the military, and total sales would reach about 18,500. After the war, H&R attempted to make the rifle more popular on the commercial market as the Leatherneck, Model 150, and Model 151, but sales were tepid.

In 1958, the USMC contracted for another quantity of the rifles, as they were adopting the M14 at that time. Several minor changes were made to the rifle, and one significant one - the safety was changed from a Reising type lever to an M1/M14 type safety located in the front of the trigger guard. This new pattern was designated the MC-58, and about 3500 were purchased by the Corps in 1958 and 1959. Serial numbers on the MC-58 rifles began at 6,000 and went to about 9,500, suggesting that 6,000 Model 65 rifles were originally purchased by the Marines during World War Two.