Article, here: http://techcrunch.com/2016/02/03/this-semi-automatic-machine-gun-is-95-percent-3d-printed/ Despite how some might read the article, the "important bits" that he had to get off the shelf are not hard to make or to come by. In the U.S., I believe it is the lowers that the government tracks and heavily regulates, and that have serial numbers. He used the printer for the lower. 3D printers aren't cheap enough yet for anyone to jump aboard, but in the next 10 or 15 years I imagine they will be if they follow similar technology trends. What do you do when you're taking gun "sales," such as from dealers, gun shows, or between private parties, and suddenly people can make their own at home? We all know how effective banning the 3d "plans" for the weapon will be (e.g. not at all, since they'll be uploaded all over the internet). As time goes on, I'm guessing the guns people can make this way will get better, not worse. So, from a regulatory standpoint, what's the best way to go after this?