An investigation by The Trace and VICE News found that criminals and extremists are increasingly using small devices called auto sears to turn semiautomatic weapons that fire only one bullet with each pull of the trigger into machine guns that can fire as many as 20 rounds per second with a single pull of the trigger. Auto sears are cheap and are only the size of a thimble, making them easy to ship or pass off as airsoft gun parts or other components. Although they have been around since the 1970s, their production and distribution had largely been suppressed by law enforcement until the last few years saw a boom in their black market availability. Now, sellers in China are supplying the U.S. market and some are also beginning to make the devices at home using 3D printers. Court records show that the devices have been used in robberies, homicides, and extremists attacks, including an attack by the Boogaloo Boys on a federal courthouse last year.
Federal prosecutions involving auto sears or devices like them have spiked. In 2017, there were only ten cases. In 2021 the number shot up to 83. The Bureau of Alcohol, Tobacco, Firearms and Explosives said it recovered 1,500 weapons modified with auto sears in 2021 after recovering only 300 in 2020. They suspect that there are far more still on the street. Jefferey Boshek, a 21-year ATF veteran in charge of the Dallas Field Division, said, “Auto sears are everywhere on the street right now. . . . They’re one of the scariest things we’ve dealt with since I became an agent.”