A tiny and cheap device called a ‘Glock switch’ lets criminals create their own machine guns

Houston Police Officer William Jeffrey knew danger lurked on the other side of the door when he arrived to serve a felony arrest warrant in September 2021.

What he couldn’t have known was how much danger.

“Deon, it’s Houston Police. Let’s do this the easy way,” Jeffrey said, as his body camera rolled.

Within seconds, a burst of automatic weapons fire pierced the door and struck his chest, ending his life. He was one of many recent victims of what law enforcement officials say is a growing threat: Handguns and rifles illegally modified with a small device to shoot like machine guns. Referred to as “Glock switches” or “auto sears,” these devices have proliferated on the streets, officials say, amplifying the impact of gun violence. Tiny, cheap and easy to install, they are being imported from China, but also are being made with 3D printers.

A modified gun used to shoot at police in Pittsburgh.
A modified gun used to shoot at police in Pittsburgh.Alleghany County District Attorney’s Office

“My father was shot more than a dozen times,” Jeffrey’s daughter Lacie told NBC News. If the shooter had been firing a regular gun, she said, “my dad could have probably gotten out of the way. He probably could have moved. But he didn’t have a chance because of the rapid fire.”

The gunman, Deon Ladet, was killed when police returned fire. Earlier this year, a man who killed the police chief in Brackenridge, Pennsylvania, fired a converted machine gun at pursuing officers before they shot and killed him. In November, a fleeing suspect shot and wounded a Dallas police officer with a modified handgun.

At the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, machine gun conversion devices have become one of the top enforcement priorities. An ATF report on guns used in crimes found that the number of machine gun conversion devices seized by law enforcement went up 570% from 2017 to 2021, and officials say preliminary numbers from 2023 show another huge increase.

Houston Police Officer William Jeffrey.
Houston Police Officer William Jeffrey.Courtesy Lacie Jeffrey

“New machine guns have been against the law in the United States since 1934, the days of Al Capone and the Tommy gun,” ATF Director Steven Dettelbach said. “But we’re seeing them all over the place … we’re talking about the rate of fire being 800 or even 1,000 or more rounds a minute. Think about how many bullets that is.”

He said conversion devices are increasing the danger to already-outgunned police officers and increasing the risk of stray bullets hitting bystanders. ATF firearms experts demonstrated the devices for NBC News at a law enforcement firing range in Washington, D.C.

“There are all kinds of different machine gun conversion devices that are incredibly deadly,” Dettelbach said. “Some of them just go on normal Glock-type handguns. This is, this is a Glock weapon, right? Doesn’t look like anything different. Right? This little square piece of plastic that comes off the back makes this into a fully automatic weapon that is capable of causing mass casualties.”

Converted handguns are extremely difficult to aim and control, he said.

A conversion device on the back of a gun.
A conversion device on the back of a gun.ATF

“Handguns are not made or designed to be fully automatic machine guns,” he said. “When a person hooks this up to fire so many rounds, there’s an extremely large kick, it pulls the weapon up. … On the street, what it means is, there’s a kid walking two blocks away, coming home from school, or a family in a park, and they may be nowhere near the actual shooting. And we’re spraying scores of bullets all over our communities and hurting and killing people.”

A former Ohio National Guard member was sentenced to almost six years in prison earlier this year in part for using a 3D printer to make conversion devices he sold online. Police found him after he made online threats to Jewish schools and synagogues where he worked as a security guard.

The ATF is trying to catch and prosecute people selling auto switches, but “we’re a very small agency,” Dettelbach said. “We don’t have a lot of resources. But what we have, we’re focused day and night at trying to keep up with, as one chief of police put it to me, the flood of the switches in our communities.”

Not every state matches federal law in making possession of the devices a felony.

Officer William Jeffrey with his daughter Lacey Jeffrey.
Jeffrey with his daughter Lacie Jeffrey.Courtesy Lacie Jeffrey

Lacie Jeffrey is among those pushing to make Texas law match the federal statute.

“If someone’s getting caught with these pieces (in Texas), it’s just a misdemeanor,” she said. “In the federal law, it’s a felony and so we’re just asking Texas to match the federal side of it. So that way, if these criminals are getting caught with these, the punishments are harsher.”

Lacie Jeffrey said she misses her father every day.

“My dad thought that he was Superman for Houston,” she said. “He thought that if he wasn’t at work, the city was going to crumble without him. He loved being able to serve his community.”

But he was more than a police officer, Lacie Jeffrey said.

“He was a father. He was a brother. He was a husband. He was a best friend. He was the everywhere man. He made sure that he was at every family function, whether it was on the East Coast or the West Coast or here at home. He loved his job, but he loved his friends and his family more and we all miss him immensely.”