When any firearm, metal or organic, 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 graphene circuits, are x-ray elusive, can easily be melted down to prevent ballistics tests, https://israelfzoak.bloggadores.com/16970532/high-production-proliferated-three-d-printed-plastic-assault-guns-on-the-way