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3D printed AR lower receiver doesn't meet expectations

One of the more interesting technologies for creating rapid prototypes and other items is 3D printing. 3D printing is capable of producing just about anything you can imagine from implantable cartilage for medical uses, to prototype parts and even weapons.

A project called Defense Distributed has been working on 3D printer files that allow users to create components to build their own guns using a 3D printer. A group of testers used a 3D printed gun part design from creator HaveBlue to produce an AR lower receiver (the lower receiver is a key component of the weapon that receives the rifle cartridge from the magazine) and headed to the gun range.

Unfortunately, it appears that recoil pressure in the completed weapon was too much for the buffer section of the 3D printed lower. The buffer is a section that separates the stock from the upper receiver reports NBC News. The part failed after firing only six shots. To make the failure even more embarrassing, the testers were using ammunition specifically designed for lower recoil.
The creator of the part claims to have printed his own and used it to fire hundreds of rounds.
While the firearm breaking in half while in operation seems to offer the potential for harm to the shooter and those nearby, the testers say that the only damage the operator faces is that of ego. When the weapon failed, the spring and buffer popped out of the tube and fell to the ground according to the testers.

Sources: NBC News, WikiWep DevBlog

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RE: RELAX! All is well. Please do not panic.
By Adonlude on 12/5/2012 12:30:57 PM , Rating: 5
No it is not the area that sees the most force, not by a long shot. The title of this article is misleading as all the most intricate and stressed parts of an AR-15 were not printed.

The explosion happens in the upper which contains a steel barrel, chamber, and bolt assembly. A bullet is loaded into the chamber which surrounds the bullet casing while the tip of the bullet extends into the start of the barrel. The bolt assembly presses in behind the bullet and is held tight for the massive 50,000ish PSI explosion that takes place then the bolt assembly slides back and is slowed by a basic spring in a buffer tube right behind it.

All this thunder and ligntning takes place in the upper. The lower is just a nice frame that the upper sits on. The lower holds a magazine, handle, trigger assembly, and shoulder stock which houses the buffer tube.

Nobody is going to be 3-D printing a gun until cheap 3-D printers are cranking out hardened steel parts on your desktop.

By Schrag4 on 12/6/2012 3:38:39 PM , Rating: 2
To be fair, I think he meant that the part where the lower broke is the part of the lower that sees the most force. The rearward force from the bolt and buffer basically "bounces off" the buffer tube, which is attached to the lower precisely where the lower failed. Think of how the buffer tube attaches. If you pull straight back on that part of the lower, since it's only attached to the lower at the "bottom" of the buffer tube, and since that printed material flexes easier than aluminum of the same thickness, that part of the lower will flex and allow the buffer tube to move downward, pivoting on the lower. IMO, no surprise at all that it failed there.

Assuming you don't dry-fire the lower with no upper attached, which can damage even standard aluminum lowers (would probably shatter this printed lower), I'd guess that the next largest force the lower sees is probably from the pistol grip. I'm sure the pin for the hammer probably exerts quite a bit of force for a very brief period of time, but that force isn't being exerted in a place where it can really snap anything off.

"Let's face it, we're not changing the world. We're building a product that helps people buy more crap - and watch porn." -- Seagate CEO Bill Watkins
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