The United States military has adopted many different firearms to be used for service over its history. There has been drastic progress made in the technology each of these weapons used, as well as how the military chose which rifle would be selected. In the United States, the biggest advances in single soldier weaponry happened throughout the twentieth century. During the start of this period, a United States military rifleman was using a bolt action Springfield 1903 rifle, and at the end of this period he was using the ultra-light fully automatic M16 assault rifle. This change in standard issue equipment did not happen overnight, and I will examine how each service rifle was developed, what led to its adoption along with its military service, and the soldiers’ opinion of each rifle. My examination will start with the Springfield 1903 leading into WWI, then transition to the M1 Garand in WWII. This was followed by the M14 at the end of the Korean War and the start of the war in Vietnam, and finish with the adoption of the M16 assault rifle for the remainder of the Vietnam War into today. Each of these rifles marked a major leap forward for United States’ weapon manufacturing as well as an improvement to the soldiers’ ability to be effective in battle. The lessons learned by the United States military after the development and deployment of these weapons helped shape the requirements for future weapons, along with the American idea of how an infantry soldier can be most effective in battle.