I don't trust plastic 3D printed guns especially with long term usage. Even with PETG plastic which is a combination PLA / ABS (two very common plastics to 3D print with) I'd still be hesitant. PETG is designed to remove the worse elements of PLA / ABS and keep the best elements of PLA / ABS at the same time or at least is intended that way overall.

Personally to get something worthwhile I'd figure I'd have to at least spend $25k to $50k on a metal 3D printer. IDK personally on this, but from what I gather to get decent quality at least especially over a long period of time this is what I figure I'd at least need.