Man creates potentially deadly bullets just for 3D-printed guns

As 3-D printed guns have evolved over the past 18 months from a science-fictional experiment into a subculture, they’ve faced a fundamental limitation: Cheap plastic isn’t the best material to contain an explosive blast. Now an amateur gunsmith has instead found a way to transfer that stress to a component that’s actually made of metal—the ammunition. Michael Crumling, a 25-year-old machinist from York, Pennsylvania, has developed a round designed specifically to be fired from 3-D printed guns. His ammunition uses a thicker steel shell with a lead bullet inserted an inch inside, deep enough that the shell can contain the explosion of the round’s gunpowder instead of transferring that force to the plastic body or barrel of the gun. Crumling says that allows a home-printed firearm made from even the cheapest materials to be fired again and again without cracking or deformation. And while his design isn’t easily replicated because the rounds must be individually machined for now, it may represent another step towards durable, practical, printed guns—even semi-automatic ones.