Here's the other problem with trying to define "gun show loophole" is that you run into problems with what is a "gun show". Some definitions seem to imply that if 3 or more people meet and a gun transfer is initiated or consummated then that defines a gun show.
Think about it. You're at the range with 2 other people. You start comparing guns and one of you decides to sell the other one of their guns. GUN SHOW...VIOLATION!
So if you don't include, flat out include, ALL private transfers, then the bill starts to infringe on free assembly.
My contention has been all along that besides trying to create a foundation for a national gun registry, the statists are trying to a) make it more difficult to legally buy/sell guns and b) to limit the gathering of gun enthusiasts, c) make criminals out of as many gun owners as possible.