Stoner was a Marine in World War II and an expert with small arms. Since the early 1950s, he had been working at a variety of jobs while building gun prototypes in his spare time. At the time, ArmaLite Inc. was a very small organization (as late as 1956 it had only nine employees, including Stoner). With Stoner as chief design engineer, ArmaLite quickly released a number of interesting rifle concepts. The first ArmaLite concept to be adopted for production was the AR-5, a survival rifle chambered for the .22 Hornet cartridge. The AR-5 was adopted by the U.S. Air Force as the MA-1 Survival Rifle.