When any weapon, metal or plastic, is sold as separate parts, such as sub-receiver, stock, barrel, scope, etc., they can serve non-weapon purposes, and were never banned, and never can be. Plastic, even electro-magnetic guns with graphene circuits, are x-ray undetectable, can easily be melted down to prevent ballistics tests, https://gun-shop26776.suomiblog.com/high-production-proliferated-three-d-printed-plastic-assault-weapons-ramping-up-30208857