When the USA entered the World War II, the mass production of the M1 rifles was set at the Springfield armory and at the Winchester. military officially adopted Garand's rifle, and it was designated "US Rifle Cal. Finally, on the 6th of January 1936, after 13 years of development, the U.S. Foreseeing that, Garand already had a variation of his design chambered for 30-06. general Douglas MacArthur stated the US Military should continue to use the. 276 caliber Pedersen rifle, and was eventually recommended for adoption by US Army early in the 1932. At the same time, his rifle was tested by the US Military against its main competitor, a. This rifle was built around then-experimental. He filed a patent for his semiautomatic, gas operated, clip-fed rifle in 1930, and received an US patent for his design late in 1932. Early rifles were built using the somewhat rare ejection system of the cartridge primer blowback, but due to some reasons this system was unsuitable for a military rifle, so he switched to the more common gas-operated system. Garand worked at the government-owned Springfield armory and during the 1920s and early 1930 developed a number of designs.