Adding an auto sear to a semi-automatic AR-15 takes a matter of minutes, says John Sullivan, the director of engineering at Defense Distributed, a DIY gunsmithing and gun access group. 3D-printing the auto sear itself would take around 10 minutes, Sullivan says, given that it's less than a cubic inch of material. "It's a single piece of plastic. It’s not even something you have to print out and assemble," Sullivan says. Because the part doesn't directly receive any of the explosive pressures of firing off rounds, it can be made of plastic and still function reliably, Sullivan says, though might break eventually. "The part atrophies. But that's the whole point of these 3D-printed parts. When the part breaks you take it out and replace it. It takes two seconds."
Of course, for the vast majority of Americans printing a drop-in auto sear is also very illegal, Sullivan points out. In the eyes of US gun control laws, the auto sear component is itself considered an automatic weapon, which are federally banned if they weren't manufactured before 1986. "The part in and of itself is a machine gun," Sullivan says. "Everyone who prints this out is committing a felony."
That hasn't stopped 3D-printable blueprints for auto sears from spreading around the internet; the files themselves are legal, after all, even if the printed part isn't. The decentralized gun access group Deterrence Dispensed six months ago released a printable auto sear file called the Yankee Boogle, an apparent Boogaloo reference. A "trailer" for the gun file's release, which includes images of printed plastic auto sears, remains online and has more than 200,000 views on YouTube. Separately, two Boogaloo members were indicted in September for boogaloo bought printed parts
