A tiny, cheap device known as a "Glock switch" or a "machine gun conversion device" allows criminals to convert a handgun into a machine gun and unleash 30-plus rounds in seconds, federal authorities say.

Officials at the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) are sounding the alarm about these devices, which can be made on a 3D printer and sometimes cost as little as 40 cents.

ATF officials took Fox News on a tour of its National Service Center in West Virginia, where they demonstrated to journalists how these machine gun devices are illegally made and the devastating damage they can inflict.

A split photo shows a handgun modified with a glock switch and a large magazine.

A handgun modified with a Glock switch and a large magazine is fired. A Glock switch allows shooters to fire thirty-plus rounds in seconds. 

Glock switches are showing up at more and more crime scenes. They allow five rounds to turn into 50 with a simple click. These conversion devices account for the majority of illegal weapons recovered in trafficking cases, ATF officials told Fox News.

An ATF report revealed that in the decade leading up to 2021, there was a 570% increase in the number of conversion devices recovered by local law enforcement.

3D printer fabricates a machine gun conversion device.

A 3D printer fabricates a machine gun conversion device.

DOJ officials, including those with the ATF, say they will now look even harder for machine gun conversion devices and teach local law enforcement how to spot them.

"Law enforcement in many instances doesn't even know what to look for always when it searches for machine gun conversion devices, because they don't look like Tommy guns," said ATF Director Steve Dettlebach.

ATF Director Steve Dettlebach holds up a machine gun conversion device.

ATF Director Steve Dettlebach holds up a machine gun conversion device.

The ATF has several examples of these conversion devices being used to kill in just the past few years. Four people were killed, and 32 were injured at a sweet 16 party in Dadeville, Alabama in April 2023. Authorities say a conversion device was used. The Justice Department says – if you've used or are even thinking of making one – don't.

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"Using MCDs is illegal. Selling MCDs is illegal and being in possession of MCDs is illegal," said Deputy Attorney General Lisa Monaco.

The contraptions are banned by federal law, carrying up to ten years behind bars.

Fox News' Max Bacall contributed to this report.