What is an AR 15? Developed by Eugene Stoner in 1957, the AR 15 rifle was built to meet the needs of soldiers following WWII. Although many have mislabeled the “AR” as meaning assault rifle, it actually stands for ArmaLite Rifle which was the manufacturing company that held the first rights of the design. It wasn't until 1959 that ArmaLite sold the rights to the AR 15 to the current owner Colt. In order to be considered an AR 15, the firearm must perform basic functions on its own without effort from the user. Upon pulling the trigger, the firearm needs to fire a single cartridge and remove the used case from the chamber. It must also load an unused cartridge into the chamber from the magazine, cock the hammer and prepare to fire a fresh round. There are two operating systems available for AR 15s, the direct gas impingement system and the gas piston system.
Direct Gas Impingement System