IOW, a homemade shotgun. Also, Straw purchasers....seems to me the illegal act is committed by the purchaser. There would have to be some other evidence of the intent and disposition beyond just the purchase.
Buy a piece of gas pipe and make a shotgun instead OF CONNECTING IT TO YOUR WATER HEATER! That’s against the law?
Not according to youtube. http://www.youtube.com/results?search_query=pipe+shotgun