Enlarge (credit: Cyrus Farivar) Since 2013, I have followed the saga of Cody Wilson, the pioneer behind 3D-printed firearms. The Austin, Texas-based digital gunsmith famously demonstrated in March 2013 that it’s possible to build the lower receiver of an AR-15 on a 3D printer. "Download this gun," he told me by phone back then. Since then, Wilson has gone on to build a one-shot pistol dubbed the "Liberator." He moved on to two generations of CNC mills that could help citizens manufacture metal guns at home.