http://www.mercurynews.com/california/ci_22249478/plastic-gun-made-3d-printer-and-test-fired
The teaser headline overstates, since actually "...the gun was built with some key parts created on a 3-D printer and fired six times before it broke."
The gun-control aspect is interesting, but the technology is fascinating! We can print 3-d objects that have moving parts.
Here's a 10-minute video where they print a bike that I think is worth watching since it talks about the technology:
http://www.youtube.com/watch?NR=1&v=hmxjLpu2BvY&feature=endscreen
Here's a 23-sec video where they just print a wrench:
There's no moving parts in the lower receiver, it just houses the moving parts.
The lower receiver is the most highly regulated part of a firearm, though; considered to be what makes it a "gun".
I'm sure we're not far off from having 3D printers and media that can create a reliable receiver.