The Bullet That Could Make 3-D Printed Guns Practical Deadly Weapons

Wired – by Andy Greenberg

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.  

The 3-D printable blueprint of Michael Crumling's test gun, with his specially designed ammunition round shown in darker grey.“It’s a really simple concept: It’s kind of a barrel integrated into the shell, so to speak,” says 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.”

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, as shown in the GIF below.


Combined with revolver components or some sort of auto-loading mechanism,Crumling believes his method could enable printing a semi-automatic weapon. “That’s the main reason I developed these, and that’s the next step,” says Crumling. “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.”

In the meantime, Crumling’s ammunition could demonstrate a controversial new upgrade to the durability of even single-shot printed guns. Law enforcement bodies around the world have responded to the threat of 3-D printed weapons by noting their unreliability. The US Bureau of Alcohol Tobacco and Firearms released a video last year showing a Liberator, the first 3-D printed weapon created by the libertarian group Defense Distributed, exploding during ATF’s test firing. Australia’s New South Wales police commissioner Andrew Scipione held a press conference last year to warn about the guns’ danger after blowing up a Liberator of its own. “No matter what end of this gun you can be on, you could die,” he warned.

Defense Distributed has responded by arguing in each case that government officials used the wrong printing methods or the wrong caliber ammunition, perhaps intending to scare gun enthusiasts away from printable weapons. But Defense Distributed engineer John Sullivan also admits the Liberator and other plastic-barrel guns take significant damage every time they fire a conventional round. Because typical ammunition uses thin brass casing, the metal deforms and transfers the round’s explosion to the gun’s plastic pieces. “That’s why a printed barrel works for only say, 10 rounds,” Sullivan says. “It just wears out.”

For now, the limiting factor to Crumling’s rounds may be the difficulty of producing them. So far he’s machined the ammunition, which he’s named the .314 Atlas based on its .314-inch caliber and the 1920s Atlas lathe he uses to make it, shell by shell.The process takes a painstaking 60 minutes per round. But the raw materials cost only 27 cents each, he says. And once the shells are produced they can be fired, then repacked with new bullets, gunpowder and primer to be shot again.

3d-gun-06Crumling’s steel-shelled rounds seem to control their explosions well enough to protect printed guns created with even the very cheapest printing techniques. “This guy has refined 3D printed firearms such that they can be reliably printed on very low end 3-D printers,” says Sullivan. “It’s so brilliantly simple. I love it.”

Despite the gun control firestorm associated with 3-D printed weapons, Crumling says he’s not particularly interested in his invention as a political provocation as much as an engineering accomplishment he wanted to share with the gun community. “I’m not an activist. I’m more of a challenge-oriented person,” he says. “This posed a challenge and that’s much more interesting to me than any political motivation.”

That hasn’t prevented him from taking some legal precautions. His test weapon contains a chunk of metal to make it legal under the Undetectable Firearms Act and has a rifled bore to comply with the National Firearms Act. Manufacturing your own ammunition is legal in the U.S., though selling it requires a Federal Firearms License. Crumling says he doesn’t plan to sell his Atlas rounds, though he’s sharing designs for the ammunition on his website. He adds that he could change his mind if enough gun enthusiasts ask to buy the rounds, in which case he’ll apply for the necessary license.

Until then, Crumling’s 3-D printing-friendly ammo will serve as a proof-of-concept—and a reminder: If gun control advocates are taking comfort in printed weapons’ impracticality, that comfort gets a little colder with every upgrade.

4 thoughts on “The Bullet That Could Make 3-D Printed Guns Practical Deadly Weapons

  1. A good idea but it makes me sad to think about having to use something so darn close to a Liberator. Hope I didn’t hurt your eyes/ears with that language, Paul; )

    I do understand that what you were thinking and what you typed were quite possibly two VERY different things! 🙂

  2. they are just reinventing the zip gun…

    and it is obvious the writer of the article doesn’t know how a firearm works.. the powder charge does not explode, it burns at the given rate to the powder type used.. that is unless your using black powder and don’t have it packed correctly, then it can detonate which usually takes the gun with it….

    but if your having to create special ammo for it then that kind of defeats the purpose of printing the thing to begin with. if you have to machine the ammo then you might as well machine a proper barrel capable of delivering accurate fire..

    if you have a hardware store or scrap yard you can knock out a zip gun in about an hour that will accept regular ammo in a lot less time and less cost than the 3d printed.. and a muzzle loading rifle using match heads as propellent and wheel weights as ammo is not to hard to make.

    and if one must still print a gun then i suggest you use a barrel liner with a plate at the back so you can use regular ammo in the thing..

    this is what the guy with the special ammo does not seam to get. make an insert to go in the gun if your going to machine anything so you can use regular ammo otherwise your stuck to how much ammo you can create and if your in a situation you can’t make more your screwed ..

    he can take the same machined shell, set it up to contain a regular bullet and mount it in the gun with a falling block plate at the back.. the shell holder has a notch at the back that accepts the sliding plate that has a hole in the center to accept the firing pin, when the shell is fired you then slide the plate out of the way and push out the spent shell, stick in new shell slide the plate back in place and then fire again.. simple, effective, and can use regular ammo that is easy to find..

    1. another way to do it would to take the same retainer/bullet he made and make it where a shell would fit in it and then have a plug that screws into the back of it to retain the normal shell.. when it is fired it can then later be reloaded with regular ammo..

      and 60min per round to make and he is supposed to be a machinist? that is painfully slow for a beginner .. shouldn’t take more than 15-20min per bullet to machine on a manual lathe like his Atlas… i got a old Shelton manual and can do things that size in 10min.. a CNC could do them in about 3-5min a piece..

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