Michael Crumling, a 25-year-old machinist from York, PA has developed a cartridge designed specifically to be fired from 3-D printed guns. It uses a thicker steel case with a lead bullet inserted an inch inside, so that the case can contain the force of the blast 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 repeatedly without cracking or deformation.

“It’s a really simple concept: It’s kind of a barrel integrated into the shell, so to speak,” said Crumling. “Basically it removes all the stresses and pressures from the 3-D printed parts. You should be able to fire an unlimited number of shots through the gun without replacing any parts other than the shell.”

The demo round is called the .314 Atlas.