Mechanical engineering student James Patrick is bound to turn some heads with his PM522 Washbear, a 3D-printed pepperbox revolver capable of firing up to 8 bullets between reloads. Except for an elastic band spring, a metal firing pin, and steel rods as detectable metal, the gun is entirely 3D-printed using ABS plastic or a durable nylon material. According to Patrick, it is the world's first functional 3D-printed repeating firearm that has been printed using a consumer 3D printer.
Patrick has been working on his gun for months and it shows in the design, which is brilliantly simple. Unlike Cody Wilson's single-fire Liberator gun, Patrick's Washbear is a revolver that makes good on its name, allowing the user to take multiple shots without reloading. Patrick uses a 6- or 8-chamber pepperbox-style cylinder that is removable. The cylinder is held in place by a simple pin at the front that can be easily removed, permitting the user to swap out a 6-round cylinder and replace it with an 8-round without modifying the gun.
Once the cylinder is loaded and in place, Patrick uses elastic bands attached to a trigger to turn the cylinder and line up the round for firing. As the user pulls backs on the trigger, the cylinder moves into place and the striker is pulled back with the trigger. The striker is equipped with a flat roofing nail as the firing pin. When the trigger is pulled back to its furthest position, it drops down slightly into the handle, allowing the striker to move forward and hit the round with the firing pin. As the trigger moves back to its resting state, the cylinder is moved off-center, a safety measure that prevents the accidental firing of the gun in case it is dropped or jostled.
In an attempt to comply with gun regulations, Patrick has added adequate detectable metal to the plastic gun using steel rods that are epoxied into the well of the grip. It remains to be seen whether this inclusion of detectable metal will be enough render the gun legal or whether the authorities will seek to have the blueprints for the gun removed from the Internet as it did with Wilson's Liberator gun when it debuted in 2013. As of the publishing of this post, you can still download the STL files for the Washbear from Patrick's website and read his five-part series that covers the design and assembly of the gun.