I have in fact been to 5 gun shows that don’t do background checks, and changed my mind about buying one I’d had my eye on when the guy behind the table opened with “I am not legally required to check your ID, just to ask if you intend to use a firearm to commit a crime, and I can’t sell to you if you say yes”. This was in Arkansas, around 2014-2015
I mean, in the US I’m pretty sure only Navy deals with shotguns, I think to prevent hull penetration? Coasties might for the same reason, but I’ve never hung out with any