If the Supreme Court rules that bump stocks aren’t machine guns later this summer, it could quickly open an unfettered marketplace of newer, more powerful rapid-fire devices.

The Trump administration, in a rare break from gun rights groups, quickly banned bump stocks after the 2017 mass shooting at a Las Vegas concert that was the deadliest in U.S. history. In the ensuing years, gun rights groups challenged the underlying rationale that bump stocks are effectively machine guns — culminating in a legal fight now before the Supreme Court.

Justices appeared divided on the issue during oral arguments in February, and they are on the clock to hand down a ruling by June. How they ultimately define machine guns will have a sweeping impact not only on bump stocks but a whole class of similar rapid-fire devices effectively banned in the U.S.

David Pucino, legal director at Giffords Law Center, said lower courts are currently treating bump stocks and similar devices like machine guns, which are banned.

“The use case for new rapid-fire devices lower courts are considering is that somebody wants to have a machine gun, and the law won’t let them have one,” Pucino said.

If the Supreme Court does overturn the ban, he said, it “would be very, very dangerous for public safety.”

Bump stocks, which gained national attention after the shooter in Las Vegas used the devices to kill 60 and injure hundreds more, are inaccurate, sporadic and difficult to control, jolting a gun back and forth. Gun enthusiasts have created new rapid-fire devices without the jolting drawbacks of bump fire.

The logic of legalization for all of the devices is basically the same: It’s not technically a machine gun. And if it’s not named, it’s not banned.

Circuit courts have come to different conclusions on whether a bump stock is legally a machine gun, and the Trump-era ban remains in place pending the Supreme Court’s ruling in Cargill v. Garland, which pits a gun dealer, Michael Cargill, against the Department of Justice.

The conservative majority of the 5th Circuit called the language of machine gun bans “egregiously ambiguous,” while the more liberal D.C. Circuit said it was the plaintiff’s definition that was “unworkable, internally inconsistent, and counterintuitive.”

If the Supreme Court undoes the bump stock ban, it would be up to Congress to decide how — or whether — to regulate rapid-fire devices, which have proliferated through the gray market since 2017. 

Some members of Congress are already pressing for action in advance of the Supreme Court decision.

Rep. Abigail Spanberger (D-Va.) and 67 members of Congress wrote a letter to Speaker Mike Johnson (R-La.) in March calling for preemptive legislation against bump stocks and other rapid-fire accessories.

“This is particularly imperative given the case pending before the U.S. Supreme Court,” which “could disrupt the current legal landscape,” the lawmakers said in the letter. 

The Closing the Bump Stock Loophole Act would limit “gun industry loopholes, as it applies to all parts and modifications that similarly increase the rate of fire by eliminating the need for each single function of the trigger.”

Speaker Johnson declined to comment on the letter from Spanberger or the GOP’s willingness to regulate rapid-fire devices.

Only one Republican — Rep. Brian Fitzpatrick (Pa.) — signed onto Spanberger’s letter, highlighting how the politics have shifted since 2017. At that time, even the influential National Rifle Association (NRA) was calling on federal agencies to review whether bump stocks were legal.

The NRA has done an about-face on that position. Writing to the Supreme Court, the organization called the Bureau of Alcohol, Tobacco, Firearms and Explosives’s (ATF) ban of bump stocks “arbitrary and capricious” and said “Congress defined ‘machine gun’ clearly, and bump stocks clearly do not fit that definition.”

900 rounds a minute and ‘100 percent legal’

In 2022, Rep. Joaquin Castro (D-Texas) wrote to ATF Director Steven Dettelbach after authorities found the shooter at Robb Elementary School in Uvalde, Texas, attempted to use a “hellfire” trigger to accelerate his AR-15’s rate of fire.

The hellfire trigger is an inexpensive, “invisible” addition to popular firearms such as the AR-15. The device creates guns with “substantially the same rate of fire as fully automatic [rifles],” Castro wrote.

Authorities found that the device malfunctioned at Uvalde. Castro worried the haunting day at Uvalde — when 19 students and two teachers were shot and killed — could have been even worse.

“The outcome in Uvalde was already devastating, and a device that effectively functions as a bump stock should be explicitly prohibited under ATF’s regulations,” Castro said.

Firequest International, which manufactures the hellfire products, currently boasts that its device “allows you to pull your gun’s trigger at up to 900 [rounds per minute], legally.”

Firequest claims its products arrive with an ATF certificate of legality and that “you can fire single, double, bursts or empty [magazines] and it is 100 percent legal.”

The ATF declined to comment on the legality of Firequest’s products or its claims about ATF certificates.

But Firequest is one seller in a larger gun enthusiast community probing for weaknesses in machine gun bans, and hellfire triggers are just one example of the vague line between what’s legal and what isn’t.

At the center of this debate is the forced-reset trigger (FRT).

Unlike a semiautomatic firearm, which requires users to release the trigger to fire again, an FRT pushes itself back into the starting position automatically, as users are still pressing the trigger down with their pulling finger.

Manufacturers of FRTs argue their products are not machine guns because the trigger still “functions” once for every round fired.

However, a shooter using an FRT fires much faster than even the fastest speed shooters could ever hope to.

So fast, in fact, that enthusiasts have made comparison videos between a real M16 machine gun and a semi-automatic AR-15 with an FRT.

Both chew through a 30-round magazine at the exact same rate and are nearly indistinguishable unless you look inside the gun.

The government argues that the “continuous” action of the shooter — holding down the trigger — effectively converts a semi-automatic gun into a machine gun.

In 2022, the ATF released an open letter advising federally licensed gun dealers that “some” FRT devices are illegal under the 1968 Gun Control Act. The ATF would not comment on what “some” may mean.

The letter hasn’t stopped manufacturers from innovating new designs that achieve forced reset, with names including the “wide open trigger,” “the super safety,” “the Alamo-15” or simply the “FRT-15.”

This has led to a game of regulatory whack-a-mole, with an ongoing cycle of sale, sanction and then confiscation from buyers, forcing manufacturers to attempt a new workaround that may fall outside the “some” distinction.

ATF spokesperson Ruth Clemens told The Hill that “ATF has significant concerns about the public safety risks posed by forced reset triggers and similar devices.”

“While ATF and the Department are taking appropriate actions consistent with the pending litigation, we cannot further comment at this time,” she added.

Spirit vs. letter of the law

When Congress signed machine gun bans into law in the 1930s, it banned any gun that fires more than one round with “a single function of the trigger.”

The Supreme Court will decide what Congress meant by “single function” almost 100 years ago. Though the court’s decision will be specific to bump stocks, it will also inform fights over rapid-fire triggers that have been bubbling up at lower courts.

In October, a federal district court in Texas ruled the ATF’s ban on FRTs is “likely unlawful” after the National Association of Gun Rights (NAGR) challenged it. 

NAGR represents the company that created the first FRT design, Rare Breed Triggers, which has since been sanctioned by the Department of Justice.

The gun rights group applied the same logic now being used to defend bump stocks at the Supreme Court, winning an injunction against government bans.

In that case, Judge Reed O’Connor said, “the definition of machinegun ‘utilizes a grammatical construction that ties the definition to the movement of the trigger itself, and not the movement of a trigger finger.’”

“The statute does not say ‘by a single pull of the trigger finger.’ Nor does it say ‘by single function of the trigger finger,’” O’Connor said.

Gun control advocates argue that a debate over “single function” misses the point of bans on machine guns.

“The Justices are aware there’s a sort of forced nature to the other side’s argument,” Shira Feldman, director of constitutional litigation at Brady United Against Gun Violence, told The Hill.

Brady, a gun-control advocacy group, has also filed a brief in Cargill.

“Is it really reasonable that Congress would have written the law such that we have to read these statutes in a way that we wouldn’t normally parse language?” Feldman said.

According to Feldman and fellow legal experts at Brady, the gun industry has been “disingenuous” in calling rapid-fire accessories legal and has sold them as “get them before … [they’re] banned” products.

“We’ve seen the gun industry do everything they can do to skirt federal regulation to increase the lethality of the weapons that they can sell to civilians, whether it’s a hellfire [trigger], a bump stock or a host of other accessories,” said Christian Heyne, chief programs officer at Brady.

“The main reason you have these is to kill as many people in this short amount of time as you can. And to victims, it isn’t important exactly how the trigger mechanism works,” added Douglas Letter, Brady’s chief legal officer.

“The point is that what Congress was trying to do [when it passed machine gun bans] was make these unbelievably dangerous weapons not a part of our civilian society,” he said.

Cargill, the plaintiff in the bump stock case, is a Texas gun store owner who sued the government after it confiscated his two bump stocks in 2018. 

He argues the ATF took up powers meant for Congress when it started to treat bump stocks like machine guns.

In a phone interview with The Hill, Cargill also said the question before the Supreme Court simply comes down to the letter of the law.

“It’s not justification enough to say that ‘it could be used in a particular crime,’ even if it was used in the worst shooting in the United States,” he said.

“It’s not about the rate of fire … this is about the action in the trigger. If I pull the trigger and one round comes out, that’s semiautomatic.”