How about printing suppressors?
I seriously doubt that would work. Suppressors need to be metal to handle the heat and pressure.
Original stereolithography prototypes were made for “show and tell” marketing demonstrations. My company made some SLA rotors for a flowmeter that we actually tested, but they did not have the long term wear properties for production use.
3D printers can make functional parts now. However, I do not think they can currently make parts strong enough to make something like an engine or a firearm that would be durable enough to have an acceptable lifespan.