When the ATF set its sights on a house in St. Louis importing MCDs this past May, it was just the latest in the agency’s efforts to get the deadly devices off the streets, here and across the country.
“MCD” stands for machine gun conversion device—colloquially known as a switch. Installed on a semi-automatic weapon, it can fire a 34-round magazine in seconds, according to Shannon Hamm, assistant special agent in charge of St. Louis’ Bureau of Alcohol, Tobacco, Firearms and Explosives. The device is a violence multiplier, and over the past few years the ATF has made blocking its spread a priority.
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Hamm says that the two most common sources of switches are domestic 3D printers and imports from overseas. The St. Louis importer had received almost 60 packages from China since 2016, declared to be everything from auto parts to plastic brooms to polyester cleaning cloths. The MCDs were imprinted with a Glock logo and the words “Made in AUSTRIA,” though they almost certainly weren’t made in Austria, and definitely not by Glock.
The suspicious packages caught the attention of law enforcement, which in May asked a judge to place a tracking device in one of them. Now the man receiving the devices is a fugitive from the law. SLM is not naming him because charges against him have not yet been made public.
Why It Matters: “Gun crimes are made much more deadly with these machine gun conversion devices,” says Hamm. The more bullets fired, the more likely an innocent bystander gets struck. According to the ATF, some communities that have reduced the number of shootings have still seen fatalities rise due to the prevalence of these devices.
And they have become common. “I don’t know a single case now that we’re doing that we don’t come across them,” he says, referring to the ATF’s investigations into violent gangs and organized crime. The demand for the devices is driven in part by a vicious cycle in which one gang outfits their guns with the switches, leading rivals to do the same. The switch itself can be a sort of status symbol, flaunted on social media.
What’s Next: With MCDs proliferating, the ATF has stepped up its efforts in kind. In September, the ATF announced an anti-MCD task force and Deputy Attorney General Lisa Monaco directed federal prosecutors to prioritize these cases. Locally, the most recent available data is from 2022, when St. Louis Police seized 27 MCDs in the city. That’s a marked increase from 2020 and 2021, when city cops nabbed only one device each year.
