3D printed firearms have faced much stigma since designers and engineers have began dabbling with different design concepts, and halfway 3D firearms in the case of 3D printed AR15 lowers. However from various conversations with law enforcement, it seems that the general professional consensus is that they are not up to the standard that they would have to be, in order to be a threat to Law Enforcement, and a benefit to criminals worldwide (criminals already have a long history of improvised firearms). Most of the 3D printed firearms out there cannot last a significant number of rounds, and are certainly not semiautomatic by themselves (users must add parts that cannot be 3D printed). In addition, they all need various pieces of metal or other material to effectively function.
However, a fellow by the name of James Patrick has tackled the problem of a semiautomatic 3D firearm in a different fashion, by making a revolver action. His design appears to be function quite well with .22LR ammunition, but my question would be for how many total rounds. He uses a nail for a firing pin, and elastic bands to provide tension for the hammer, trigger and cylinder. The design of the pistol grip/trigger guard/ trigger looks to have some inspiration from the Kimber Pepperblaster while the actual cylinder holds 8 or 6 (different versions) rounds of .22LR. The cylinder is removable, there doesn’t appear to be much of a barrel as it takes on a pepperbox design, and the reset looks insane!
The revolver version is called the “Washbear”
He also has a single shot version, called the “Songbear”.