"Light, precise and with little recoil, the Colt Armalite Rifle-15 Sporter hit the market in the early 1960s as the first civilian version of the military’s M16 rifle. What set it apart was, much like its military counterpart, the inventor Eugene Stoner’s patented gas operating system, which allowed for rapid fire and reloading. The weapon could easily handle a 20-round magazine, was easy to disassemble and was marketed, in one of Colt’s early advertisements, to hunters, campers and collectors. Billed as “America’s rifle” by the National Rifle Association, the AR-15 is less a specific weapon than a family of them. When Mr. Stoner’s rights to the gas system expired in 1977, it opened the way for dozens of weapons manufacturers to produce their own models, using the same technology. The term AR-15 has become a catchall that includes a variety of weapons that look and operate similarly, including the Remington Bushmaster, the Smith & Wesson M&P15 and the Springfield Armory Saint. Over the ensuing decades, as the American military modified the M16’s exterior to allow for accessories such as sights, grips and flashlights, the civilian market followed. Today, gun enthusiasts consider the AR-15 the Erector Set of firearms."