Andy Greenberg writes: 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.
“This is a building block for the future of 3-D printed firearms that will enable people to develop semiautomatic and—if you had the proper legal paperwork—even fully automatic weapons.”
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.
“It’s a really simple concept: It’s kind of a barrel integrated into the shell, so to speak. 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.”
Last week, for instance, Crumling shot 19 rounds from a 3-D printed gun of his own design created on an ultra-cheap $400 Printrbot printer using PLA plastic. (He concedes his gun isn’t completely 3-D printed; it uses some metal screws and a AR-15 trigger and firing hammer that he bought online for a total of $30. But he argues none of those parts affected the gun’s firing durability.) Though the gun misfired a few times, it didn’t suffer from any noticeable internal damage after all of those explosions. Here’s a time lapse video that shows 18 of those shots.
When the top of Crumling’s gun shattered in an earlier test, he determined that the breakage was caused by the shell’s movement, not the explosion inside of it. So in his most recent gun design, the roof of his gun’s chamber is left open. That allows the shell to eject itself. Read the rest of this entry »