While I like the show, (let's face it, it's no worse than most of the crap they air these days), I've often wondered about the licenses they hold, or should hold, for some of the stuff they mess with. The last show I watched they had a large, fully functional WW II Howitzer they were firing with live ammo they handloaded with 6 pound "bullets" they seated on a hydraulic press.
This type of weapon would require a destructive device license, in addition to an FFL to own it and manufacture parts for it. I'm sure there are other licenses required to manufacture all the Class III stuff they make and buy and sell as well. They are also always rigging stuff up with explosives for greater television effect when they shoot at it. This kind of thing always happens on "American Guns" as well.
Actually, I find "Sons Of Guns" to be a bit more believable than "American Guns". With that ex cop flying off in a $ Million dollar + Bell Jet Ranger helicopter, with a duffel bag filled with tens of thousands in cash to "get the first crack" at some millionaires gun collection. I mean come on, let's get real here. Who puts guns up for sale, then has every gun shop in the state playing "Cannonball Run" to get there to buy them? Anyone with that type of collection is going to sell through a professional auction house. Not simply put word out on the street, then wait for someone to show up in a helicopter, and land in your backyard with a wheelbarrow full of cash to buy them. Let alone a retired cop running a local gun shop. I guess that's why they call it "reality TV". It would never happen in reality.