Mechanical engineering student James Patrick recently uploaded a video to his YouTube channel showing off the fully functional PM522 Washbear .22LR revolver that he designed and 3D printed. With the exception of the firing pin, a few elastic bands that act as springs and the legally required amount of detectable metal, the entire gun including the body and cylinder is completely 3D printed. This is, to my knowledge, the very first functional repeating firearm ever made entirely (This doesn’t count, it has metal barrel inserts) on a desktop 3D printer.
The frame of the PM522 Washbear was designed to hold either a six or eight shot pepperbox revolver, however the six shot is printed in a more durable nylon material while the eight shot is printed in ABS with steel chamber liners for extra strength. Both barrels will fit in the same gun frame, so they are interchangeable. All of the stl files have been optimally orientated by Patrick in order to maximize the strength of the material and prevent failure. For instance, the gun frame is printed flat on its side while the revolver is printed standing up. By putting them together the frame is strong enough to contain the the pressure of firing and keep the cylinder layers from splitting.
In contrast, the 3D printed Liberator handgun designed by Cody Wilson holds and fires only a single bullet, and doesn’t always survive for a second shot. If what Patrick says about the PM522 Washbear is accurate, this is a significant upgrade from the Liberator, although he does warn that the gun isn’t intended for repeated usage. Patrick also suggests that subsonic ammunition is the best choice of ammo because it won’t break the sound barrier when it fires, resulting in no shock wave as the slug leaves the chamber.