The AR-15 , the model used by a gunman in Connecticut last week, is the civilian version of the military’s M-16 and M-4. In surveys, about 50 percent of buyers say they own AR-15s for target practice; 30 percent for hunting; and the rest for personal protection. Despite often being called a fringe gun by critics, the AR-15 is the most popular gun sold in the U.S. today, according to gun dealers. Roughly 220,000 were sold in 2010, after peaking at more than 300,000 immediately following Obama’s election. The previous assault weapons ban lasted from 1994 through 2004. It defined an assault weapon as any gun that was: semi automatic, meaning one round is fired per each pull of the trigger, and used a detachable magazine; and featured any two of the following attributes:

• a folding or telescopic stock;

• a pistol grip;

• a bayonet mount;

• a flash suppressor; or,

• a grenade launcher.