The Colt AR-15 was introduced in 1963. It is the semi-automatic version of the United States military M16 rifle. The first mass production version was the Colt AR-15 Sporter, in .223 Remington, with a 20-inch barrel and issued with 5-round magazines.[2] Over the decades, Colt has made many different types of AR-15 rifle and carbine models, including the AR-15, AR-15A2, AR-15A3, AR-15A4, and many other models.