The Wiki Weapons Project performed the first live test of a printed AR-15 assault riffle, a new milestone on the company's roadmap towards the creation of the first blueprint of a fully 3D printed gun. On the test bench was a 3D printed lower receiver for an AR-15, basically the trigger and the handgrip, the only part of the gun that you can't buy without a license. The rest of the gun was put together with off-the-shelf parts that are easy to come by. The test reveals the endurance isn't too great, the 3D printed part fell apart after firing just six rounds. Full details at Popular Science.
The team thinks the problem was recoil, which caused the plastic to become unhinged. The threads connecting the receiver to the stock worked just fine--the o-ring just snapped. The group explains further in their blog post.
It’s worth noting that a previous, less powerful gun, a .22 caliber pistol also manufactured with a 3-D printer, was far longer-lasting. The .22, which we reported back in July, fired 200 rounds in testing.