The .AR-15 is a lightweight, air-cooled, gas-operated semi-automatic rifle designed for civilian use. Originally developed in the late 1950s by Eugene Stoner for the ArmaLite company, it has become popular for various applications, 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. It typically fires .223 Remington or 5.56×45mm NATO cartridges, providing a balance of power and manageable recoil. Its versatility and ease of use have contributed to its widespread adoption in the United States.