I wonder how many of them are BATFE spooks trolling for suckers??
Here is S.C. you have to pass through an inspection area staffed by the local SD and/or PD before your allowed inside. All firearms are checked to be sure they're legal and not loaded then gets a zip tie through the action. (Judging by the bucket of mixed ammo on the table there must be a fair number of idiots showing up with loaded guns.) Packs and bags are checked for contraband as well. This includes loaded magazines.