"Significant advances in three-dimensional (3D) printing capabilities, availability of free digital 3D printer files for firearms components, and difficulty regulating file sharing may present public safety risks from unqualified gun seekers who obtain or manufacture 3D printed guns," warns the bulletin compiled by the Joint Regional Intelligence Center. The bulletin refers specifically to Defense Distributed, a nonprofit company started by a University of Texas law student, which has successfully made and fired a 3D gun whose only metal parts are the bullets and a small firing pin. Some 100,000 plans for a gun called "The Liberator" were downloaded in just...