We don't yet know for certain if Stephen Paddock used an automatic weapon when he killed at least 59 people, including himself, and injured hundreds of others in Las Vegas on Sunday night. If you know anything about US gun laws, though, this should have at first seemed unlikely — after all, automatic weapons are some of the few guns that are supposed to be banned or, at the very least, strictly regulated in America.
The reality is more complicated. That's because, as is all too typical with US gun laws, the automatic weapons ban has some pretty big loopholes. And that makes it possible that the rapid fire heard in the videos of the Las Vegas shooting came from a fully or effectively automatic weapon.
Automatic weapons are what many Americans think of as machine guns. These are guns that can continuously fire off a stream of bullets by simply holding down the trigger — making them very deadly. Semiautomatic weapons, by contrast, fire a single bullet per trigger pull. The difference between an automatic and a semiautomatic effectively translates to firing hundreds of rounds a minute versus dozens or so in the same time frame.
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Under federal law, fully automatic weapons are technically legal only if made before 1986, when Congress passed the Firearm Owners' Protection Act. So it's now illegal to manufacture new automatic weapons for civilian use.
That gets us to the first loophole: If you have an automatic weapon from before 1986, it was grandfathered through the law. So it's still legal to buy, sell, and exchange these kinds of weapons, including in Nevada, as long as they're a few decades old — although with some extra hurdles that don't apply to other types of firearms, such as registering fully automatic guns with the US Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) and paying a special tax, with the risk of additional penalties if someone doesn't comply.
There are more than 630,000 of these guns in circulation, according to federal data.
The second major loophole is that it's legal to sell and buy modification kits that can convert semiautomatic weapons into effectively automatic ones. The Associated Press explainedhow one of these modifications, the "bump stock," works:
The device basically replaces the gun's shoulder rest, with a "support step" that covers the trigger opening. By holding the pistol grip with one hand and pushing forward on the barrel with the other, the shooter's finger comes in contact with the trigger. The recoil causes the gun to buck back and forth, "bumping" the trigger.
Technically, that means the finger is pulling the trigger for each round fired, keeping the weapon a legal semi-automatic.
Paddock had 12 bump stocks, Ken Dilanian reported for NBC News, among an arsenal of 23 guns at the hotel he shot people from and 19 at his house, at least some of which were AR-15– and AK-47–style weapons. But it's not clear if the modifications were actually used during the shooting, as investigators are still piecing together what happened.
It's also just one kind of modification. There are others, including a crank that replaces the trigger — turning a gun into what a gun aficionado channel on YouTube called "a mini Gatling Gun." And it's still possible to make illegal modifications that turn guns into fully automatic weapons, as Andy Greenberg explained at Wired.