Okian Warrior writes "Adding to the 3-D printed gun/rifle controversy, Delta-V Engineering built a Full-auto Gauss gun (aka 'machine gun'), capable of firing 15 steel bolts from its magazine in less than two seconds. At 3% the muzzle energy of a .22, it's still in the prototype stage. Bullets are made from turned-down nails, and the gun uses no chemical propellants. The builder has posted the design notes online. Video of the gun in action is pretty interesting."