People misunderstand 3d printed guns. We use mostly normal gun parts bought anywhere, but legally the pistol handle is considered the gun, and the most popular commercial ones have been plastic for decades. So 3d print that glock frame and put a glock slide on it and you’ve got a cheap glock (and outside of like 3 States, that’s totally legal).

There’s fairly large 3d printing gun communities, mostly because it’s just fun to build things.

3d printed silencers are much more rare / fragile because those are illegal to make without ATF approval and silencers need to withstand heat and pressure, so the typical plastic can’t withstand prolonged use.