ETA: If the transaction crosses state lines, an FFL must be involved. Where that FFL must be located depends on whether it's a long gun or handgun.
The gun show loophole is simply a myth. The rules apply at gun shows the same way they do everywhere else.
A gunfight is not the time to learn new skills.
If you ever have a real need for more than a couple of magazines, your problem is not a shortage of magazines. It's a shortage of people on your side of the argument. -- Art Eatman