The internet videos are alarming to some, thrilling to others: Gun enthusiasts spraying bullets from AR-15-style rifles equipped with an after-market trigger allowing them to shoot seemingly as fast as fully automatic weapons.

The forced-reset triggers so concerned the federal Bureau of Alcohol, Tobacco, Firearms and Explosives that it ordered the company making them to halt sales only months after they began in 2020, declaring the devices illegal machine guns.

Rare Breed Triggers, founded in Florida and now based in Fargo, North Dakota, said the ATF was wrong and kept selling its FRT-15 triggers, setting the stage for a legal battle now in federal courts in New York and Texas.

The triggers are the latest rapid-fire gun accessories to draw scrutiny from government officials worried about mass shootings and police officer safety, joining bump stocks, which were banned by the Trump administration after the 2017 mass shooting in Las Vegas that killed 60 people, and cheap parts called auto sears that can make a pistol fire as if it were fully automatic.

“The defendants are illegally selling machine guns, plain and simple, with conversion devices that transform AR-15 type rifles into even more lethal weapons suited for battlefields, not our communities,” Breon Peace, the U.S. attorney for the Eastern District of New York, said when he sued Rare Breed in January, accusing the company of fraud.

The lawsuit, being heard in federal court in Brooklyn, claims Rare Breed failed to get ATF approval before selling the devices and defrauded customers by telling them the triggers are legal. Rare Breed denies any wrongdoing.

Meanwhile, the National Association for Gun Rights sued the ATF in a federal court in Texas this month, challenging its classification of the FRT-15 as a machine gun. The suit was filed in the 5th U.S. Circuit Court of Appeals, the same district where the bump stock ban was struck down in January after other courts had upheld it.

Both the bump stock and forced-reset legal battles involve how to apply the National Firearms Act of 1934 — a law passed in part to try to curb gangland violence — as modified in 1968 and 1986.

The law bars the public from owning machine guns, which are defined as firearms capable of firing more than one shot, without manual reloading, by a single pull of a trigger, or “any part” that converts a weapon into a machine gun.

On the firing range, guns equipped with either bump stocks or forced-reset triggers certainly look and sound like machine guns. In court filings, the ATF said testing on the FRT-15 triggers showed their rate of fire can meet or exceed that the military’s M-16 machine gun, which can fire 700 to 970 rounds a minute.

But under the law, the key to whether a part turns a weapon into a machine gun isn’t the rate of fire, but whether or not multiple rounds can be fired with a single pull of the trigger.

Rare Breed’s owner, Kevin Maxwell, and its president, Lawrence DeMonico, both appeared in federal court in Brooklyn this month to argue their device is not a machine gun because it forces the trigger to return to the start position after each shot, so only one shot can be fired with a single “function” of the trigger.

“I mean, it fires fast. It’s reasonable for people to ask questions,” DeMonico said. He later added, “But it’s not that it fires fast. It’s how it fires fast that matters. So did I know that it was going to be controversial? Sure. But did I think I was doing anything wrong? No. I still don’t believe I was doing anything wrong.”

The ATF says constant finger pressure on an FRT-15 trigger will keep a rifle firing like an automatic, and the fact that the trigger is moving doesn’t make it legal.

The triggers were designed to work in AR-15-style rifles and take only minutes to install. Rare Breed has sold about 100,000 FRT-15s, generally at just under $400 apiece, raking in nearly $38 million, the ATF said.

U.S. District Judge Nina Morrison issued a temporary restraining order in January barring Rare Breed from selling more of the triggers while the legal dispute plays out. Rare Breed said it was essentially forced to stop business in March 2022 after the ATF seized its inventory from its manufacturer in Utah.

The ATF has also been asking people who bought the forced-reset triggers to voluntarily turn them over to the agency.

Maxwell and DeMonico did not return email messages from The Associated Press seeking comment. The ATF declined to comment on the New York and Texas lawsuits.

During his testimony, Maxwell questioned why the ATF approved another company’s forced-reset trigger, the Tac-Con 3MR, which he said fires about as fast as the FRT-15.

Another kind of rapid-fire trigger, the binary trigger, was used earlier this month in a shooting in Fargo that killed a police officer and wounded two others and a civilian. The binary trigger, which allows a weapon to fire one round when the trigger is pulled and another when it is released, is legal in most states and at the federal level.

The binary trigger and bump stocks work differently than forced-set triggers. Bump stocks, for example, are frames or components added onto the back of semi-automatic weapons that use the recoil from each shot to help fire the next round.

The federal court in New Orleans that ruled bump stocks weren’t an illegal machine gun conversion noted the decision didn’t apply to certain types of the devices equipped with springs or other mechanics help shooters fire automatically.

One of the allures of popular AR-15-style rifles is that owners can customize them in any number of ways, said Robert Spitzer, an adjunct professor at the College of William & Mary School of Law and professor emeritus at the State University of New York at Cortland who has studied gun control and gun politics.

Rapid-fire gun parts, he said, are “about trying to find civilian workarounds that give you weapons that fire like a military weapon.”

As for forced-reset triggers, Spitzer said, “Why on earth would anybody want this thing? There seems to be ... two reasons: One is if you want to do a whole lot of damage out in society, which is a goal that no sane person would say is justifiable. And the other is because some people find this loads of fun.”

Morrison, the judge in the Brooklyn case, is expected to decide in the months ahead whether to keep her freeze on Rare Breed’s triggers in place while the legal dispute continues in her court. A trial date has yet to be set in the Texas case.