I have read somewhere (Topacios book maybe) that the barrel is already considered a firearm. There are a lot of aftermarket barrels and conversion kits around. Should such be found in my possession (inside my house assuming there is a search warrant for unlicensed firearms), can I be charged with illegal possession? How would one legalize aftermarket barrels or conversion kits? Aftermarket barrels and conversion kits do not have serial numbers on them how would one regulate these?