Mass shootings such as the one at a Texas church on Sunday in which 26 people died have focused public attention on weapons and accessories — and some of what is legal may surprise you.
The gunman, Devin Kelley, bought his Ruger AR-15 legally after the Air Force failed to enter his court-martial in a federal database. The gunman in the Las Vegas shooting Oct. 31, Stephen Paddock, had 23 legally purchased guns including an AR-15 in the hotel room where he perched as he mowed down 58 people at a music festival below.
As the AR-15 has exploded in popularity in recent years, gadgets to modify and improve its performance — legally — have also grown. Here are a few:
Las Vegas police thought Paddock had automatic weapons despite the fact that he used semiautomatic rifles that require a separate trigger pull for each shot. He had bump stocks, which use the recoil of each shot to accelerate the next trigger pull, on 12 of the weapons, according to the Bureau of Alcohol, Tobacco, Firearms and Explosives.
But another widely available accessory is the trigger crank, which allows the shooter to spin a mechanism attached to the trigger like reeling in a fishing pole to fire three times per rotation. The rapid firing sounds like a Civil War-era Gatling gun.
100-round drum magazine
Standard magazines for the AR-15 hold 30 rounds. But a 100-round drum magazine is available to allow more shooting before reloading.
The magazine is a pair of circular containers that resemble a pair of headlights or bongos hanging below the rifle.
A 1994 federal law that prohibited large-capacity magazines expired in 2004. But a handful of states still limit magazines to 10 or 15 rounds.
A review of 62 mass shootings from 1982 to 2012 by Mother Jones magazine found large-capacity ammunition magazines were recovered in half the cases. The gunman in the July 2012 movie theater shooting in Aurora, Colo., James Eagan Holmes, had a 100-round magazine.
Multiple magazine holders
Another way to keep firing for a longer period of time is to have multiple magazine holders. While each magazine still holds 30 rounds, a half-dozen magazines could be attached side-to-side to allow the shooter to quickly pull one magazine and shift to the next after each magazine is emptied.
For a change in ammunition and firepower, a modified AR-15 with its .223-caliber barrel could have a 12-gauge shotgun mounted beneath.
When the ammunition finally runs out, rifles can be equipped with knives called bayonets attached to the tip of the weapon for hand-to-hand combat. Bayonets were commonly used in World War I and II.
One of the more creative extensions for the AR-15 is a chain-saw bayonet.
Night-vision and thermal-vision scopes
Scopes atop the rifle help the gunman aim the weapon through sight or with the advantage of a laser that pinpoints where a bullet is projected to strike.
After the early morning Orlando nightclub shooting in June 2016, police sought more night-vision scopes to see targets in darkness. Thermal-vision scopes also help a gunman track a target by heat against a cooler background.