"Colt Manufacturing, which had the military contract for the M-16, recognized that there could also be a civilian market for this rifle. So they developed what they called the AR-15, which was actually the original developmental designation of the rifle. The only difference between these rifles that are sold on the civilian market and the rifles that are issued to our soldiers and soldiers all over the world is that the purely military rifle is capable of firing what's called fully automatic fire. That means if you pull the trigger and hold it down, the gun will continue to fire until it expends all the ammunition in what is known as the magazine, the thing that holds the bullets. Machine guns have been outlawed in the United States, effectively, for civilian use since the mid-1980s. So what these guns need to be configured to be are semiautomatic. That means you must pull the trigger for each round fired. There's a question about rate of fire which the industry and the NRA and other advocates of having these guns in civilian hands make, and it goes like this: Well, the military guns are fully automatic, therefore they're technically machine guns, but the civilians guns are not. They're semiautomatic, and therefore they're not assault rifles. That's a distinction without a difference, as many writers on the gun side noted in the early 1980s, when even the industry called them assault rifles, until they became involved in unfortunate incidents...The reason I say it's a distinction without a difference is that the trigger can be pulled at a very rapid rate in semiautomatic fire, and it's actually more accurate...in automatic fire the gun has a tendency to rise upward, to travel. If you go to shooting ranges where automatic weapons are used, you'll often see, in the ceiling, bullet holes because you pull the trigger and the characteristic sounds of - bbrruppp - the gun will rise. Semiautomatic fire doesn't do that, which is why the military encourages soldiers to shoot semiautomatic rather than automatic whenever possible."