This Simple, Legal Add-On Lets an AR-15 Rifle Fire 900 Rounds Per Minute

Frank Geiman fires an AR-15 rifle at the Knob Creek Gun Range in West Point, Kentucky.

Photo by JOHN LOK/AFP/Getty Images

Crime is Slate’s new crime blog. Like us on Facebook, and follow us on Twitter @slatecrime.

Hey, it’s Monday, and I’m back with more on the AR-15, the hugely popular semi-automatic rifle that has been in the news ever since it was used by Adam Lanza in December to kill 26 people at Sandy Hook School. (Note: I have received several unconvincing emails claiming that Lanza did not, in fact, use the AR-15. Show me your evidence if you’ve got it, guys, because every single reputable source I’ve seen—including the Connecticut State Police—says that Lanza used an AR-15-style rifle in the attacks, brought two pistols into the school, and had a shotgun in the trunk of his car. Grainy YouTube videos do not count as “evidence.”)

Why are AR-15-style rifles so popular? As put it, “the AR-15 is kind of the gun-dweeb’s version of Linux: All kinds of modifications can be made to it.” It’s relatively simple for an enthusiastic marksman to customize the rifle to his specifications—adding a scope and other optics, swapping in a new grip, or trigger, or barrel. These modifications are more or less benign. But there’s another change that’s more problematic: For a few hundred dollars, you can convert the semi-automatic AR-15 into a rifle that can simulate automatic fire. And it’s perfectly legal.

To understand how this works, you first need to know about a process called “bump firing.” When you bump fire a semi-automatic rifle, your non-shooting hand pulls the rifle forward until the trigger hits your rigid trigger finger, thus firing the rifle. Then, recoil sends the rifle bouncing back and forth against your rigid trigger finger, causing it to keep shooting at an accelerated rate, simulating automatic fire.

You generally bump fire from your hip, and you can’t really aim the rifle, which makes the technique kind of frivolous. If your fingers don’t work and you can’t squeeze a trigger, bump firing is a godsend. Otherwise, bump firing is only useful if you want to waste a lot of ammo fast.

At least that was the case until a couple of years ago. That’s when a company called Slide Fire Solutions introduced a replacement rifle stock called the SSAR-15 that, for $369, allows you to bump fire your AR-15-style rifle from your shoulder while still retaining accuracy and control. The stock, in the simplest terms, is the part of the rifle you hold and brace against your shoulder. According to the Slide Fire website, “unlike traditional bump firing, the Slidestock allows the shooter to properly hold the firearm and maintain complete control at all times. As a result of the forward movement required to discharge each round, the shooter naturally corrects their point-of-aim for each shot and prevents recoil from pushing the firearm’s muzzle upward in an unsafe direction.” Or, as the subhed more concisely puts it, the SSAR-15 lets a shooter “unleash 100 rounds, in 7 seconds.” A product review at a site called Guns America notes that the SSAR-15 “installs in one minute with no special skills.”

I could explain this a bit more, but it’s probably best just to watch a couple videos.

If you’re like me, you had two reactions after watching those videos: “Holy shit,” and “There’s no way that can be legal.” But it’s completely legal. Prominently linked on the Slide Fire website is a letter from the Bureau of Alcohol, Tobacco, Firearms and Explosives, confirming that the Slide Fire stock “has no automatically functioning mechanical parts or springs and performs no automatic mechanical function when installed,” and hence “is not regulated as a firearm under Gun Control Act or the National Firearms Act.” As far as I can tell, it would’ve been legal under the now-expired Federal Assault Weapons Ban, too. To be covered by the AWB, an AR-15-style rifle with a detachable magazine also had to have at least two of the following five features: “(i) a folding or telescoping stock; (ii) a pistol grip that protrudes conspicuously beneath the action of the weapon; (iii) a bayonet mount; (iv) a flash suppressor or threaded barrel designed to accommodate a flash suppressor; and (v) a grenade launcher.” The SSAR-15 isn’t any of those things.

In its letter to ATF, Slide Fire apparently argued that its product was intended to help people with bad hands. And, indeed, the jolly old woman at the end of the Slide Fire promotional video looks thrilled to have rediscovered the joy of firing a rifle really fucking fast. But the Slide Fire website indicates that the SSAR-15 is being marketed to an able-bodied demographic. (The top of the site features a huge picture of a zombie, and the words “Prepare. They won’t kill themselves….”) It’s impossible to watch those videos and not think about using the SSAR-15 to mow down enemy hordes.

A lot of people have argued that gun-control advocates fixate on modern rifles like the AR-15 not because they’re inherently more dangerous than shotguns, revolvers, or bolt-action rifles, but because they look scary. There’s some truth to that argument. But it’s also true that’s a lot easier to modify a modern rifle into something that really is scary. You can’t send hundreds of rounds per minute down range with a bolt-action rifle. Though my thoughts on gun control are evolving and subject to change, I’m still generally against it. But I also think that we need to have as much good information as possible about the guns in our midst, both about what they do and what they can be made to do.