When any gun, metal or organic, is sold as separate parts, such as sub-receiver, stock, barrel, scope, etc., they can serve non-weapon purposes, and were never outlawed, 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://gun60110.alltdesign.com/high-production-produced-3d-printed-plastic-assault-weapons-ramping-up-35110119