I think I have broke the code. I’ve read and pondered and come up with this. Double barreled 410/45 long Colt. I wanted 20 gauge but that puts me over the 50 caliber limit. Barrels and chambers will be less than 12” total. Pistol grip. Rifled barrels. ( This was giving me fits until I thought about barrel length. We’re not talking about 3-6” of rifling. Must have a twist BUT it doesn’t have to be deep.) No Government form anything. No AOW. No tax stamp. All from scratch. No modified gun parts. That’s my theory anyway. If I’m thinking wrongly, please tell me.