It's a popular rifle among U.S. gun owners. And it's become especially popular as the weapon of choice in American mass shootings.
The massacre in an Orlando, Florida, nightclub that left 50 dead and dozens more wounded has once again prompted calls for a ban on the AR-15, the weapon used in the worst mass shooting in modern U.S. history.
The Orlando massacre "is more horrific evidence of the unique lethality of the AR-15," Joshua Koskoff, a lawyer representing the families of those killed and injured in Sandy Hook, Connecticut, said in a statement. "It is no wonder that this weapon was chosen by today's shooter, as it has been by so many before him, and as it undoubtedly will be again."
In December 2012, Adam Lanza used a Bushmaster XM15 to kill 28 children and adults at the Sandy Hook Elementary School before taking his own life with a Glock pistol.
The latest massacre also elevated a long-running political debate about banning so-called assault-style weapons for civilian use.
The National Shooting Sports Foundation, which represents gun manufacturers, declined a request for an interview "until more information is known."
The AR-15, developed from the U.S. military's M-16 rifle, is manufactured by dozens of U.S. companies, including major gun makers like Smith & Wesson, Sturm Ruger and Remington Arms. Unlike the military version, the AR-15 is not fully automatic, meaning the shooter must pull the trigger each time to fire a shot. But like the military version, the guns are capable of firing many rounds of ammunition quickly, and can be reloaded rapidly.
Sales have been brisk for U.S. gun makers in the last decade. The number of total firearms made topped 10 million in 2013, the latest data available from the Bureau of Alcohol Tobacco and Firearms. That's more than double the industry's output in 2008.