AR-15–style rifle

Lore & Background

The AR-15 design originated from the ArmaLite AR-10 battle rifle, invented by Eugene Stoner in 1956 for use in the 7.62 NATO caliber. A lighter weight selective fire variant was designed in 1958 for military use and designated the ArmaLite model 15, or AR-15. Due to financial problems and limitations in manpower and production capacity, ArmaLite sold the AR-15 and AR-10 designs and trademarks to Colt's Manufacturing Company in 1959 after the military rejected the design in favor of the M14. In 1964, Colt began selling its own improved semi-automatic version known as the Colt AR-15. After most patents expired in 1977, many firearm manufacturers began producing copies under various names, though Colt retained the trademark to the AR-15 name.

The letters "AR" have multiple attributed origins: ArmaLite's website states it stood for "ArmaLite Rifle"; Eugene Stoner's business partner Jim Sullivan said it stood for the first two letters of the company's name; Stoner's daughter and son-in-law said it stood for "ArmaLite Research". A common misconception is that "AR" stands for assault rifle or automatic rifle. From 1994 to 2004, the Federal Assault Weapons Ban restricted the sale of the Colt AR-15 and some derivatives in the United States. In 2009, the term "modern sporting rifle" was coined by the National Shooting Sports Foundation as a marketing term for modular semi-automatic rifles including AR-15s.

The AR-15 design features a gas-operated, rotating bolt combined with an integral piston, patented under U.S. patent 2,951,424. A distinctive two-part receiver (upper and lower) allows for modular construction and easy substitution of parts. The lower receiver alone is legally defined as a firearm under United States federal law, though this definition has been disputed in conflicting court rulings. The standard gas system vents unburned powder residue into the receiver, which can accumulate and cause malfunctions; some AR-15–style rifles use an alternative short-stroke gas piston design borrowed from the ArmaLite AR-18.

Reader's Guide

The AR-15–style rifle's significance stems from its modularity and the vast aftermarket parts ecosystem, which has led to it being called "the Swiss Army knife of rifles," "Barbie Dolls for Guys," or "LEGOs for adults." Individuals with basic mechanical aptitude can often substitute parts without needing a gunsmith. The lower receiver can be bought stripped, allowing end users to install their own fire control group and lower parts kit. The upper and lower receivers are attached by two removable pins, enabling easy caliber changes by installing a different upper receiver assembly. Some models feature folding or collapsible stocks, and a few manufacturers have made "bufferless" bolt carrier systems that allow firing while the stock is folded. The rifle's popularity is partially attributable to active restrictions or proposals to ban or restrict them. Promoted as "America's rifle" by the National Rifle Association of America, AR-15–style rifles have gained infamy due in part to their use in high-profile mass shootings, placing them on the frontline of the U.S. gun control debate. Under US law, barrel length and overall length restrictions apply, and many manufacturers offer AR-15–style pistols with stabilizing braces to avoid classification as short-barreled rifles.

Did You Know?

• The letters 'AR' in AR-15 have been attributed to 'ArmaLite Rifle', the first two letters of the company name, or 'ArmaLite Research'.
• Colt's Manufacturing Company is the sole manufacturer able to label their firearms as 'AR-15' due to trademark ownership.
• The AR-15 design uses a two-part receiver (upper and lower) attached by two removable pins for easy disassembly and modularity.
• The lower receiver alone is legally defined as a firearm under US federal law, though this has been disputed in court rulings.