First, I appreciate this thread. We don't get a lot of info about this method... I just went to my shotgun choice webpage in the US and it says, "With the number of incoming orders being at an all time high, it is taking much longer than usual to process orders and payments." Unless I'm missing something, we should be able to purchase these so long as we don't have some law enforcement red flag on our backs.
I also checked out the NRA "Shooting Illustrated" detailing US laws on shotguns, rifles... Seems extra paperwork is required for a piece with barrel 18-inches or less (or 26-inches or less overall--"SBSs require a $200 NFA tax stamp and special paperwork..."), but I don't understand why any of this prohibits us from buying...
Of course, they add the classical caveat about criminal or mental health records. What am I missing?
P.S. I'm not adding links because I don't know if that violates some kind of TOS.