A man known as "ThreeD Ukulele" on YouTube has posted a video that shows him (or a colleague) test firing a small rifle (named the "Grizzly" after a Canadian tank) that he claims was constructed by parts he printed on a 3D printer. If his claims turn out to be true, it will mark the first known instance of a rifle being constructed in such a way.
In the video, a man can be seen affixing the barrel to the rifle (which appears to be made of a white plastic) then exiting off-screen to fire the rifle from a safe distance via string tied to the trigger. The man then returns to view after the shot has been fired to inspect the condition of the rifle. He reports that the .22 caliber bullet fired successfully but a portion of the barrel split as did the receiver.
Printing guns using expensive 3D printers has been in the news of late after a man who goes by the name Cody Wilson created blueprints for printing a handgun which he claimed he had personally test-fired. Since private citizens are not allowed to own such weapons in Canada, ThreeD Ukulele (aka CanadianGunNut on the DEFCAD forums) modified the blueprints for the "Liberator"—the name Wilson gave to his printed gun. Small arms rifles are allowed for hunting of small game in Canada, so CanadianGunNut added a longer barrel. He's one of the lucky few that have access to a 3D printer—a Stratasys Dimension 1200es where he works and is allowed to pursue personal projects as well.
Thus far, as can be seen in demonstration videos, guns produced by 3D printers aren't nearly of the same quality as those produced by professional arms makers—the printed rifle in the video, for example, isn't much better than one made from a copper tube and fired by striking with a hammer. What appears to be the reason for concern, of course, is what the future may hold. Higher quality guns printed by ordinary citizens would not only be untraceable, they could be made of materials that could easily pass through metal detectors at airports and other public venues. Worse perhaps, might be the government's inability to stop the process—laws enacted to prevent the creation, distribution or downloading of blueprints would be exceeding difficult to enforce as would preventing the printing of the product at a private location.
Explore further: Files posted online to 'print' working handgun