When any weapon, metal or plastic, is sold as separate components, such as sub-receiver, stock, barrel, scope, etc., they can serve non-weapon functions, and were never outlawed, and never can be. Plastic, even electro-magnetic guns with carbon circuits, are x-ray undetectable, can easily be melted down to prevent ballistics tests, https://gunsinternational82444.ttblogs.com/19437849/mass-produced-3d-printed-plastic-assault-guns-on-the-way