When any firearm, 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 banned, 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://gundam59012.mybloglicious.com/36145231/mass-produced-3d-printed-plastic-assault-guns-ramping-up