'Bump-Stocks' Helped Las Vegas Shooter Kill Quickly. Here Are the Other Devices That Make Guns More Deadly

From his vantage point 32 floors up, Stephen Paddock had his pick of any shot at more than 20,000 people. This was not a spur-of-the-moment mass killing, but a methodically planned execution. The retired accountant hired a room at the Mandalay Bay hotel, armed himself with 23 firearms, including rifles bearing a likeness to the AR-15 used by U.S. troops, and smashed two windows, giving him a bird's-eye perspective that would allow him to cause maximum damage—all the while remaining out of view.

Part of Paddock's plan, officials said, was the modification of weapons from semi-automatic guns into fully automatic ones that could rapidly dispose of bullets at a pace—10 shots a second—and so could mow down concertgoers before they could make their escape from the Route 91 Festival below. Some converted semi-automatics can fire as many as 800 rounds per minute. Though it would likely decrease accuracy, 20,000 people spread out across the festival grounds provided ample targets over a wide area. Paddock killed 59 people and injured 527 more in what is the deadliest shooting in U.S. history.

Fully automatic weapons have been banned in the U.S. since 1986, but there are permissable attachments that allow legal guns to fire at the same clip with one pull, enabling gun enthusiasts like Paddock to soup up their weapons and to cause such carnage. Here are three items that are still legal and that gunowners can use to modify their semi-automatics, along with a work-around.

"Bump-Stocks"

Officials told the Associated Press that Paddock was armed with two "bump-stocks," a readily available device. The bump-stocks, also known as a "slide fire," can be bought for as little as $99.

Whereas a semi-automatic requires the trigger to be pulled after firing each round, a semi-automatic rifle with a modified bump-stock would only require one pull.

The spring mechanism of the bump-stock keeps pulling the trigger over and over without requiring extra pulls by the holder of the weapon. This effectively allows one pull of the trigger to take place, even though the trigger is actually being pulled for each round by the bump-stock.

The modification means that the rifle used is still legal and not an outlawed fully automatic weapon—even though it acts like one.

The removal of the need to pull the trigger after every round is a crucial difference in gunfire frequency. The one pull on a modified semi-automatic rifle can allow for an entire magazine to be unloaded without pause.

Trigger crank

In the immediate aftermath of the attack, gun experts said that Paddock may have used a trigger crank both because of the likelihood that he had used a semi-automatic to carry out his attack, and also because of the speed at which he fired.

The device, also known as a "gat crank," can sell for as little as $40 online and be sent in the mail.

The device literally bolts to the trigger guard of a semi-automatic and allows the user to fire the weapon considerably more often by engaging the trigger more quickly. It dramatically increases the rate of fire from dozens of rounds a minute to hundreds.

Paddock had so many guns in his Mandalay Bay hotel room that he could have potentially swapped guns to get around their stalling or overheating.

Auto-sear

Sears, like trigger cranks and bump-stocks, are readily available online.

This piece allows a fully automatic weapon to function. According to gun retailer Hallowell & Co., the sear holds "the hammer back under the tension of the mainspring. When the trigger is pulled, the sear moves out of its notch, releasing the hammer and firing the gun."

Semi-automatics can be altered with the sear of a fully automatic with just a drill and some handiwork, converting its firing mechanism to that of an assault rifle, and therefore rendering it faster and more dangerous—but also illegal.

As gun expert Sean Davis pointed out on Twitter, the modification to a full automatic, if used by Paddock in Las Vegas, would have required a new sear, as well as other parts of the assault weapon.

Or, they can just buy an automatic weapon anyway

If gun enthusiasts want to own an automatic legally and to bypass the modification of a semi-automatic, they can just buy one themselves, according to Wired Magazine.

A loophole allows anyone to buy an automatic rifle provided it was in private ownership by a family member before the weapons were outlawed in 1986. If a family member owned the gun before then, an individual can buy the rights to the automatic weapon at a hefty price, usually thousands of dollars more than the modification route.

They are outlawed in some states, but Nevada, where Paddock carried out his attack, does not ban the weapons. The state even allows unlimited ownership of semi-automatics that can be modified, as authorities appear to believe is the case in the Las Vegas shooting.