Is it frowned upon to go into the actual gun show with a firearm and a For Sale sign in a state where it is unregulated (WI)? Should that person stay outside near the door?
My opinion is that it's fine to conduct private sales on the show floor as long as you don't:
1) Interrupt a conversation between a buyer and a dealer to try to sell the buyer *your* gun instead.
2) If another private seller is trying to sell a gun to a dealer, don't jump in with an offer on the gun until the dealer has declined and turned the seller away.