title: Plastic guns? Not so fast! link: https://onemoretech.wordpress.com/2013/05/10/plastic-guns-not-so-fast/ author: phil2nc description: post_id: 4776 created: 2013/05/10 15:19:26 created_gmt: 2013/05/10 19:19:26 comment_status: closed post_name: plastic-guns-not-so-fast status: publish post_type: post

Plastic guns? Not so fast!

Very timely opinion piece in The Register by Lewis Page right now. As usual the kicker is in the subtitle. 'Liberator': Proof that you CAN'T make a working gun in a 3D printer: No need to pry this piece of crap out of my fingers. While not exactly your run-of-the-mill hoax, all the hype over plastic guns made with a 3D printer seemed from the beginning to be just slightly on the other side of P.T. Barnum's "Egress". The fact that the law student entrepreneur's site was finally shut down by an order from the U.S. State Department only adds color to an already technicolor story.

People are missing one important point about the "Liberator" 3D-printed "plastic gun": it isn't any more a gun than any other very short piece of plastic pipe is a "gun".

How true. As is this excellent description of the physics involved:

When the nail hits the cap in the cartridge base in a Liberator, the expanding gas likewise pushes the lead bullet off the end of the cartridge and down the "barrel" pipe. Much of the gas leaks past due to the loose fit and soft material of the "barrel". The lump of plastic with the nail (probably) stops the cartridge case spitting out of the back, which is pretty easy as the bullet pops out of the extremely short, basically smooth* "barrel" almost immediately with very little push from the gas required. Most of the cartridge's hot gas spills out of the muzzle without getting a chance to do any work on the bullet, which is the main reason the cruddy "barrel" doesn't (always) come to bits on the first shot and the cartridge case (probably) doesn't just spit backward into the user's face.

And this very apt comparison with a near analogue:

It's a bit better than holding up a cartridge in a pair of pliers and banging the cap with a centrepunch or similar, but not much.

Like those sportsmen who insist they have some rational basis for toting 30 round magazines along on a deer hunt, in the final analysis this plastic gun really is a ludicrous bust, justifying Lewis's conclusion that:

So what we have here is not, as everyone is saying, proof that 3D printers can be used to make guns. It's proof that they can't, and that 3D printing at the moment is basically pretty useless.

I really need to get my personal blog up and running again to avoid wasting space on this sort of thing here.

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