The way it works is that you create the untraceable part at home. You buy the rest of the parts—none of which are traceable as parts—and voila! AR 15. Your very own assault rifle and you didn't have to leave the comfort of your survivalist shed. The lawful work-around is that you cannot "sell" untraceable lower receivers for guns, but there ain't no law for making one!

Milling gun metal has always been something that only professionals and real hobbyists were involved in. Not anymore:



In fact, the process of legally milling a metal lower receiver is easier than it sounds. Using the Ghost Gunner to carve a lower receiver from a raw block of aluminum would be a lengthy, complex process. But the firearm community has long traded in so-called “80 percent lowers,” lower-receiver-shaped metal pieces that sell for as little as $80 and are roughly 80 percent finished—They only need to have a few holes and cavities milled out to become the body of a working gun. The bureau of Alcohol Tobacco and Firearms has defined that 80 percent line as the closest an object can come to a regulated rifle without legally qualifying as one. But precisely finishing the last 20 percent of a lower receiver has still required access to a milling machine that typically costs tens of thousands of dollars.

He gleefully named a design for an AK-47 magazine after Senator Dianne Feinstein, “to commemorate a personal failure of Feinstein’s to take away semi-automatic weapons.” Wilson has been criticized by gun-control advocates, including Senator Charles Schumer and Representative Steve Israel, both of whom have discussed the need for legislative counters to printable guns. While ardent gun-rights advocates are often cast by their opponents as myopic, uneducated, or somehow out of step with the times, Wilson is a bumptious, telegenic twenty-five-year-old who calls himself a crypto-anarchist; he and his collaborators hope that new technologies like bitcoin and 3-D printing will do nothing less than abrogate government, returning power to individuals and small sovereign communities. To him, 3-D printing presents “a world where you can have a firearm if you want. This is a world of equality.” What’s notable about this kind of talk is how divorced it is from any practical reality. Wilson coolly deflect questions about actual gun violence, in particular the Sandy Hook massacre, shifting into a higher register loaded with intellectualized abstractions. (During a Vice podcast, he noted his willingness to engage even more aggressively in the gun-control debate after Sandy Hook, using it to attract more attention for his vision than competing 3-D-printed gun projects.) Unlike the N.R.A., Wilson doesn’t practice politics; he practices political theory, as he does in the Vice documentary, wearing Ray-Ban sunglasses and cruising to a rented warehouse in his silver BMW, talking about concepts like “socialism from below” or dropping references to French theorists like Jean Baudrillard and Pierre-Joseph Proudhon. Gun-death statistics are not part of the rhetoric. He doesn’t want to “get bogged down in the numbers.”

This is part of a larger anarchist mission Defense Distributed and Cody Wilson are involved in I suggest you read the articles linked. It is both interesting and frightening. It really illuminates the sophomoric pseudo-intellectual flaws of the libertarian movement. It also shows that the practicality of their anti-government rhetoric is non-existent. On the one hand, they are democratizing gun ownership, and on the other, they are creating a world that is willfully deaf to all of the damage guns have done and continue to do.

I have updated the article to represent the correct information. As was pointed out in comments, the device is a milling machine and not a printer. The rest of the op does not change as a result of that. I appreciate the comments and the corrections.