Bump Stocks

On October 1, 2017, a man with an arsenal of weapons fired down from two hotel rooms upon a crowd at the Route 91 Harvest music festival in Las Vegas, killing 60 and wounding over 400 others, in what remains the worst mass shooting in modern U.S. history. First responders said the gunfire sounded like it was coming from an “automatic firearm,” but as law enforcement later learned, the shooter had actually barricaded himself in his hotel rooms with 14 AR-15-style rifles equipped with bump stocks to simulate fully automatic fire.

A bump stock is a replacement shoulder stock for semi-automatic rifles, particularly AR-15s and AK-47s, that drastically increases the weapon’s rate of fire to mimic a fully automatic machine gun’s — leading to significantly more victims in a mass shooting while serving no legitimate purpose for, say, hunting or home defense.

How bump stocks work

A bump stock works by harnessing a semi-automatic rifle’s recoil energy to continue firing. With such a device installed, the rifle can slide forward and backward within the bump stock. To fire, the shooter holds the bump stock against their shoulder while keeping their trigger finger stationary on the bump stock’s “trigger ledge.” The shooter then grips the front half of the rifle as they normally would and pushes forward until their trigger finger engages the trigger. After firing one shot, the rifle reciprocates into the bump stock and returns forward to “bump” into the shooter’s stationary trigger finger to fire again and again. This is known as “bump firing.”

In this way, a shooter can fire an entire magazine’s worth of ammunition in seconds — firing up to 800 rounds per minute — just like a fully automatic machine gun.

The bump stock rule

Machine guns, and the parts used to create them, have been highly regulated — and thus difficult for civilians to own — since the passage of the National Firearms Act (NFA) of 1934, and the Firearms Owners’ Protection Action (FOPA) of 1986 forbids civilians from owning machine guns manufactured after May 19, 1986.

Federal law defines a “machine gun” as “any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger. The term shall also include…any part designed and intended solely and exclusively, or combination of parts designed and intended, for use in converting a weapon into a machinegun.”

When the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF) first considered the legality of bump stocks, the agency determined that some bump stocks were considered “machine guns” because they used an internal spring to allow shooters to fire more than one shot per trigger pull. But between 2008 and 2017, the ATF issued several determination letters advising that bump stocks that do not use springs would not be considered machine guns, including those popularized by Slide Fire Solutions for AR-style weapons, which were used by the Las Vegas shooter.

In the aftermath of the Las Vegas shooting — the deadliest in modern U.S. history — the Trump administration directed the ATF to enact a new rule that went into effect in March 2019 and banned all bump stocks, concluding that the devices were themselves machine guns because they “allow a shooter of a semiautomatic firearm to initiate a continuous firing cycle with a single pull of the trigger.” In the rule, the ATF noted that its prior determinations were missing key legal analyses and clarified that a bump stock makes a gun fire “automatically”: “[W]hen a bump-stock-type device is affixed to a semiautomatic firearm, the device harnesses and directs the firearm’s recoil energy to slide the firearm back and forth so that the trigger automatically re-engages by ‘bumping’ the shooter’s stationary finger without additional physical manipulation of the trigger by the shooter.”

Opposition to the rule

The NRA admitted that bump stocks “should be subject to additional regulations” after the Las Vegas shooting, stopping short of supporting an all-out ban. But other groups, such as Gun Owners of America (GOA) and the Firearms Policy Coalition (FPC), challenged the ban in multiple courts, and on January 6, 2023, the Fifth Circuit Court of Appeals struck down the ban, concluding that the ATF had exceeded its authority in interpreting and enforcing machine gun statutes. That case, Garland v. Cargill, is now before the U.S. Supreme Court with oral arguments scheduled for February 28, 2024. (Read Everytown’s amicus brief here.)

For now, the federal ban remains in place for every state but Mississippi, Louisiana, and Texas, and several states and Washington, D.C., have enacted their own laws to prohibit bump stocks.

gun industry support for bump stocks

The largest manufacturer of bump stocks was Slide Fire Solutions, which ceased production in April 2018 before the bump stock rule went into effect. Other companies, such as FosTech Outdoors and Bump Fire Systems, attempted to sell their own competing designs, but Slide Fire successfully defended its patent, held by owner Jeremiah Cottle, in court.

According to the company, Slide Fire’s sales exceeded $10 million in 2010, its first year in business. Slide Fire was also an exhibitor at the Shooting, Hunting, Outdoor Trade (SHOT) Show, the largest gun industry trade show, from 2012 to 2017.

Cottle has since created a new entity, the American Bump Stock Company, to resume selling bump stocks in the states where they are currently legal.

Larry Keane, senior vice president and general counsel of the National Shooting Sports Foundation (NSSF), the gun industry’s trade association and the sponsor of the SHOT Show, has argued the ATF overstepped its authority in banning bump stocks and predicted that Cargill could lead to the ATF’s ghost gun and arm brace rules also being struck down. According to Keane, “The Fifth Circuit’s ruling is more than a question over a firearm accessory. It gets to the heart of the matter. Can the ATF — working on behalf of a president — rewrite law on their own? The court says it can’t. That is the responsibility, and the role, of Congress.”

Large gun manufacturers have mostly remained silent regarding bump stocks, though they support groups like the NSSF, GOA, and FPC. Palmetto State Armory, an assault weapon manufacturer that has marketed products to political extremists, published a blog post decrying the bump stock ban as not only a “scary concept,” but one that is unconstitutional and tyrannical. The blog post’s author even suggested that the government be overthrown for the bump stock rule by providing a link to the Declaration of Independence, which he called “instructions on what the founders thought should happen to tyrannical governments.”

bump stock recoveries

While the Las Vegas shooting is the only known mass shooting involving bump stocks, dozens of law enforcement recoveries also highlight the danger these rapid-fire devices pose. An Everytown analysis has identified 45 cases (shown in the table below) dating back to 2016 where bump stocks were recovered from people with felony convictions, drug dealers, and attempted mass shooters, among others.

Of the 45 cases:

• Five involved individuals who were arrested for planning mass shootings using rifles with bumps stocks, targeting a high school, synagogues and a Budweiser facility, a sorority, a police department, and the George Bush Foundation;
• 15 involved drug trafficking;
• 14 involved convicted felons in possession of firearms;
• One involved a car bomber who was later found with several illegal firearms as well as a bump stock, and two involved individuals found with explosives;
• 10 involved individuals illegally selling firearms; and
• 37 involved individuals found in possession of illegal firearms, including bump stocks and silencers.

The disturbing details of these cases show that criminals seek out bump stocks to enhance their lethality. In one case, an ex-National Guardsman in Columbus, Ohio, employed to provide security to local synagogues and Jewish schools began making antisemitic and violent statements online and threatened to attack synagogues and a Budweiser facility. Columbus police searched his residence and seized firearms, explosives, a 3D printer, ammunition, and more. A search of his vehicle found body armor, night-vision goggles, and a large quantity of ammunition. After being charged with state crimes, he was released on bond but was then arrested on federal charges for making and selling ghost guns, short-barreled rifles, a bump stock, and auto sears for Glocks and AR-15s.

In another case, a self-identified “incel” was arrested for plotting to shoot women at a local university in Ohio. When police searched his vehicle, they found a rifle with a bump stock attached, several loaded magazines, body armor, and boxes of ammunition. Inside his residence, police found a Glock-style 9mm ghost gun. He later pleaded guilty to one count of attempting to commit a hate crime, which is punishable by up to life in prison.

Finally, in Kentucky, a man harassed students online with “racially motivated” language and used Reddit to announce that he was planning a school shooting before purchasing an AR-15 with a bump stock, high-capacity magazines, ammunition, and body armor. Thankfully, federal agents were able to arrest him before he could carry out his attack.

more deadly innovations

• Rapid-Fire Triggers
• “Glock Switches” and Auto Sears
• Assault Weapons and High-Capacity Magazines