The M1917 Browning machine gun is a heavy machine gun used by the United States armed forces in World War I, World War II, Korea, and to a limited extent in Vietnam; it has also been used by other nations. It was used at the battalion level, and often mounted on vehicles. There were two main iterations of it: the M1917, which was used in World War I; and the M1917A1; which was used thereafter. The M1917, which was used on some aircraft as well as in a ground role, had a cyclic rate of 450 rounds per minute; the M1917A1 had a cyclic rate of 450 to 600 rounds per minute. In 1900, John Moses Browning filed a patent for a recoil-powered automatic gun. Browning did not work on the gun again until 1910, when he built a water-cooled prototype of the 1900 design. Although the gun worked well, Browning improved the design slightly. Browning replaced side ejection with bottom ejection, added a buffer for smoother operation, replaced the hammer with a two piece firing pin, and some other minor…