>Some states still don’t even have background checks at gun shows

As much as the media loves to spout out "gun show loophole", the gun show part is more or less irrelevant; It's "private seller vs FFL".

A private sale, in a majority of states, doesn't require a background check. If you want to buy from an FFL, however, you need to go through a background check, and that's federal law. The latter applies even if you are at a gun show, meaning that anyone legally in the business of selling guns has to background check you even if you're a friend or next door neighbor.

And technically private sellers aren't supposed to be selling guns for business/profit, though the interpretation of that is up for debate; rather, they can downsize their collection.