The AR-15 is a lightweight, air-cooled, gas-operated semi-automatic rifle. Originally designed by Eugene Stoner in the late 1950s, it was intended for military use but has since become popular among civilians for various purposes, including sport shooting and hunting. The rifle is known for its modular design, allowing users to customize it with different accessories and components. The AR-15 operates using a direct impingement system, which means that gas from the fired cartridge is used to cycle the action. This design contributes to its accuracy and reliability. Due to its versatility and ease of use, the AR-15 has become one of the most widely owned rifles in the United States.