alt Hacker NewsPeople normally don't make guns that are entirely 3d printed. Homemade guns often get the parts exposed to highest stresses commercially.
Fwiw, when I paid attention to my local police department's released body cam vids, maybe around 1/3 of the guns they showed as evidence were polymer80s (edit: which I mistakenly assumed were 3d printed, but it turns out they aren't so feel free to disregard that fun fact)
Polymer80 aren't 3d printed. They were injected molded as non-receivers and then the customer has to subtract some extra materials.
Polymer80 is defunct but still sold under a slightly different modified mold that someone mysterious somewhere owns and is selling through some other companies("76%" instead of 80%)