A buddy of mine at work is building an AR. The upper he has is NOT New York State legal -- it has a bayonet lug and a removable brake. So he can't put it on a post-ban lower without it being an illegal firearm. His son in West Virginia has a pre-ban lower and my friend wants to buy a post-ban lower and trade lowers with his son. That way, he'll have a pre-ban rifle that is legal. Should he go through an FFL since it's an out-of-state trade? Would they both need FFLs to handle the transfer?