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The 411 On The Bump Stocks Everyone’s Talking About After Las Vegas


“Bump stock” is the word of the week following the reprehensible shooting in Las Vegas. Here’s a guide to the trending gun topics.

What Is Bump Firing?

Sunday night’s shooter was able to launch as many bullets as he did because of a trick called bump firing. Bump firing is to semi-automatic shooting as Olympic luge is to a plastic saucer sled. To bump fire, the shooter braces the gun against his hand rather than his shoulder. Then he pushes the gun into his trigger finger to fire. This allows the recoil of the shot to move the entire gun, including the trigger, against the finger of the shooter. This imitates the rapid firing of an automatic weapon. This guy explains and demonstrates:

The unbraced rapid firing means a big loss in accuracy. So why is this even a thing? Because it’s fun to shoot fast. It’s a range trick with range toys; nothing more. Accuracy can be somewhat improved with a bump stock. The stock mechanizes the bumping action so the shooter can brace the weapon against his shoulder like usual. Here’s an AR-15 tricked out with a bump stock:

Why Are Bump Stocks Legal?

Briefly, because they don’t make a gun fully automatic.

When a semiautomatic gun is ready to fire, the hammer is cocked and held in place by the sear. Pulling the trigger releases the sear, allowing the hammer to fall, igniting the cartridge. Some of the energy of the shot is used to push the bolt to the rear, which cocks the hammer once more. The sear catches the hammer and holds it cocked. To fire again, the trigger must be released for it to reset so it can be pulled again.

When a fully automatic gun is ready to fire, the hammer is also held back by the sear. When the trigger is pulled, the sear is released, and that action releases the hammer. The hammer falls and ignites the cartridge, pushing the bolt to the rear, and cocking the hammer. But the fully automatic sear catches the hammer only momentarily, then lets it fall again as long as the trigger is held to the rear. Only when the trigger is released will the sear catch and hold the hammer, preventing it from falling on the firing pin.

The rapid firing action is accomplished internally by means of the full auto sear and firing group. By law, semi-auto guns sold in the United States are not allowed to be “easily convertible” to full-auto. The full-auto firing sears and firing groups are themselves illegal to own in all but the rarest instances.

So a bump stock doesn’t turn a semi-auto into a full-auto. But it does assist a shooter in increasing the rate of fire of a semi-auto. There are only two ways to do that: learn to move your finger really fast, or use the recoil energy of the gun to move the gun really fast against your trigger finger. The bump stock is an external mechanism that only approximates full-auto functionality.

Did the Obama Administration Really Make Bump Stocks Legal?

In 2006 (during the George W. Bush presidency), the Bureau of Alcohol, Tobacco, and Firearms (ATF) reversed an earlier decision allowing the sale of a spring-loaded bump stock, called the Akins Accelerator. This is called a reclassification—that is, they reclassified the device as a full-auto conversion kit. The company was required to hand over its customer list, and those customers had to surrender the springs in the stock to the ATF.

In 2010 (during the Obama presidency), the ATF determined that a bump stock called the Slide Fire did not fully automate a semi-automatic gun: “[W]e find that the ‘bump-stock’ is a firearm part and is not regulated as a firearm under Gun Control Act or the National Firearms Act.” This type of bump stock was the one the Las Vegas shooter used.

Why did the ATF see no problem with the Sure Fire as opposed to the Akins Accelerator? Best guess is that it’s because the Sure Fire doesn’t have springs.

Where Does the Gun World Stand on Bump Stocks?

The NRA can be thought of as the establishment branch of the Second Amendment lobby. Their official statement relating to the Las Vegas shooting allowed for examining existing laws regarding firearm parts:

“Despite the fact that the Obama administration approved the sale of bump fire stocks on at least two occasions, the National Rifle Association is calling on the Bureau of Alcohol, Tobacco, Firearms and Explosives (BATFE) to immediately review whether these devices comply with federal law. The NRA believes that devices designed to allow semi-automatic rifles to function like fully-automatic rifles should be subject to additional regulations.”

However, the Gun Owners of America, who brand themselves as tougher-minded and more absolutist in their defense of the Second Amendment, issued a statement arguing that the tragedy in Las Vegas does not occasion new legislation. Another GOA statement opposes a ban on bump stocks, pointing out, “Bump stocks were approved by the ATF during the Obama administration to help gun owners with disabilities fire their weapons.”