<Li> Picatinny rails, which allows the use of various scopes and sighting devices </Li> <P> The Colt AR - 15 is a lightweight, 5.56 × 45mm, magazine - fed, gas - operated semi-automatic rifle . It was designed to be manufactured with extensive use of aluminum alloys and synthetic materials . It is a semi-automatic version of the United States military M16 rifle . Colt's Manufacturing Company currently uses the AR - 15 trademark for its line of semi-automatic AR - 15 rifles that are marketed to civilian and law - enforcement customers . </P> <P> Colt started selling the semi-automatic version of the M16 rifle as the Colt AR - 15 in 1964 . 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 . 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 . </P> <P> The AR - 15 is frequently the target of those advocating restricting access to guns in the United States . Although the sale of new AR - 15s was banned by the Federal Assault Weapons Ban from 1994 to 2004, Colt continued to sell legally compliant versions known collectively as "Colt Sporters" and "Colt Match Target rifles" during that period . </P>

When was ar 15 made available to the public