There are three basic kinds of firearms; a handgun, a rifle, and a shotgun. Also there are two different categories of guns, a semi-automatic firearm, and an automatic firearm. A semi-automatic firearm fires one bullet each time the trigger is puller and automatically loads another bullet in the chamber for the next pull of the trigger. An automatic firearm, also called a machine gun, continuously fires bullets as long as the trigger is held down. People buy these firearms for multiple reasons like protection, crime, sports, and hunting game. In 2009 a survey was giving nationwide and it was determined that the United States has a population of 307 million people and, based on production data from firearm manufacturers, there are roughly 70-80 million civilians owning one in the United States as well as forty-forty five% of American households.