Just read this uplifting story from Wired Danger Room:
Late last year, a group of 3-D printing gunsmiths developed a key component for an AR-15 rifle that anyone with a 3-D printer could download and make at home. The problem: It only lasted six shots before snapping apart. Now the group is back with a new and improved receiver that can fire more than 600 rounds.
Defense Distributed demonstrated the receiver — the base of a gun that includes the trigger mechanism — in a video posted this week to the group’s blog. Its arrival comes the week Congress returned from vacation to debate a series of potential gun regulations. In the video, dozens of bullets contained in a high-capacity drum magazine are seen being fired by the printed receiver. (The magazine was shoved into the printable receiver, itself attached to traditional rifle parts.) It’s also the first printable receiver to fire .223 caliber high-pressure rifle rounds without breaking. An earlier versionfired low-pressure .22 caliber cartridges.
It’s important to note that fully 3-D printed guns don’t exist yet. So far, activist groups like Defense Distributed and individual hobbyists have produced only partially printed weapons — usually, printed magazines.
Here's the video: