There is no “loophole”. A “loophole” would mean that there is some legal exception to something that would normally be the rule. An FFL has to check your background, period, including at a gunshow. In some states a person who is not in the business of selling guns can sell you a gun without taking you to an FFL to get a background check. Some states have extra rules for gunshows NONE have less, NONE have a “loophole”.
Oh, and surveys of felons in prison find that they practically never get there guns at gun shows.
Crowder is brilliant.