There's a few more links inside the following stories. Pretty amazing stuff.

Have­Blue report­ed­ly used a Strata­sys 3D print­er to craft the part, assem­bled it as a .22 pis­tol and fired more than 200 rounds with it.

The tester then attempt­ed to assem­ble a rifle with the part and a .223 upper receiv­er but had “feed and extrac­tion issues.” The prob­lem may not in fact be with the 3D-print­ed part, though, as the issues remained when a stan­dard alu­minum lower was used.

blog story

3D printed AR -15

links don't work

So he printed a lower receiver (the most important part) and bough the rest of the stuff from a gun store, Still a cool idea. I am sure there would be 3D print schematics for less complex firearms. Like this thing that the allies gave to the French resistance in WWII http://en.wikipedia.org/wiki/FP-45_Liberator