A proposed federal ban on assault-style weapons is endangered by the grown of 3-D printing of guns, says the Washington Post. Making guns for personal use has been legal for decades, but doing so has required machining know-how and a variety of parts. With 3-D printers, users download blueprints from the Internet, feed them into the machine, wait several hours and voila. “Restrictions are difficult to enforce in a world where anybody can make anything,” said Hod Lipson, a 3-D printing expert at Cornell University and co-author of the new book, "Fabricated: the New World of 3D Printing. “Talking about old-fashioned control will be very ineffective.”

It is unclear how many people are trying to print their own gun parts and magazines. Cody Wilson, a University of Texas law student who is leading the ideological and technical campaign for 3-D printed guns through an organization called Defense Distributed, said blueprints have been downloaded hundreds of thousands of times from his group’s Web site. Wilson’s group has posted several videos to YouTube of AR-15s firing rounds with 3-D printed high-capacity magazines and lower receivers, the part that includes the firing mechanism and is the only regulated portion of the gun if it’s bought over the counter.