MrSeb writes "An American gunsmith has become the first person to construct and shoot a pistol partly made out of plastic, 3D-printed parts. The creator, who goes by the name HaveBlue and is an AR-15/M16 enthusiast, has reportedly fired 200 rounds with his part-plastic pistol without any sign of wear and tear. HaveBlue's custom creation is a .22-caliber pistol, formed from a 3D-printed AR-15 (M16) lower receiver, and a normal, commercial upper. In other words, the main body of the gun is plastic, while the chamber — where the bullets are actually struck — is solid metal. ... While this pistol obviously wasn't created from scratch using a 3D printer, the interesting thing is that the lower receiver — in a legal sense at least — is what actually constitutes a firearm. This means that people without gun licenses — or people who have had their licenses revoked — could print their own lower receiver and build a complete, off-the-books gun." Here come the illegal shapes. Note that the legal fiction of receiver-as-firearm is true in the U.S., but may not be in other jurisdictions, and that no gun license is required in most of the U.S. to purchase or possess a semi-automatic weapon.