Have some trinkets from a 3-D machine made out of white ceramic materials five years ago. The machine reputedly cost over $300K and the supplier indicated that they were developing sintered materials for the same process. I don't know where the technology stands today but for something as intricate as a revolver or semi-auto, additional machining and polishing more than likely would be required. The machines have their uses for modeling, etc. but utility was in question back then.