Exactly.
30.06 is not valid at gun show, it not valid on govt property, and even if it were valid when checker gives you the gun back to enter show, you get "effective consent" to carry on the property.
It's not the fact that it's a gun show that makes the 30.06 invalid, it's the fact that it's held in a government owned building. A gun show in a privately owned facility can post all it wants, in which case we can choose to go or not, but there's no question as to the legality of it.
I might be mistaken because I've never carried anything into a gun show, but I thought the LEO's inspected all the weapons to make sure they are clear and then put a zip-tie on them to prevent firing. You're not allowed to reload your weapon and stick it in your IWB holster after the LEO gives it back to you.