The NSSA rules for Skeet and Sporting Clays are very clear....
a. no shot sizes bigger than 7 1/2's ....for a lot of reasons ...shot fall range being the primary issue.
b. No gun can be loaded ..until the shooter is on the shooting station. A gun is considered to be loaded - when you have any part of any shell in any gun. That means a shell in a magazine of a pump gun or a semi-auto makes it a "loaded gun" ... or an empty shell left in the chamber of a gun ( makes it a loaded gun ).
You cannot walk around a gun club ...whether its for Trap, Skeet, 5 Stand or Sporting Clays ....with shells in the magazine of a gun ...or it is a serious safety violation. It may not be a violation of - general gun safety from an NRA perspective ....or in a field when you're hunting birds...but its a clear violation for these games ....and its not "range specific" ...its a rule published nationally.
c. the loading of more than 2 shells in the gun shall not be allowed at any time. In some cases where you only have a single target - you may only load 1 shell. In Sporting Clays, 5 Stand, and Continental Trap it is ok to load 2 shells ..and fire 2 shells at a presentation of a single target ...and the target is dead, if you hit it with either shell.
But you can never load 3 shells in a magazine...or ever move around, off of the shooting station, with any shells in your chamber or your magazine...in and out of your vehicle, the grounds, parking lot, etc ...all actions have to be open, no shells in the magazine or chamber.
At many gun clubs ...even at a handgun range....I may be allowed to have a full magazine in a gun ...only if its in a holster. I am not allowed to take that gun from my holster....either empty, or with a mag in it - empty or not - let alone with a round in the chamber ...unless I am on the firing line. Guns have to remain cased ...put the case with the gun in it, on the firing line ...put your holster on ...step to the firing line, and then put the gun into your holster. No-one wants guns being waved around ...when they might be loaded ..or when they're empty. Its the same philosophy on a Trap, Skeet, 5 Stand or Sporting Clays range.
When I uncase a gun at the back of my vehicle at a shotgun club...in the parking lot...the first thing I do, is make sure its empty ...and lock the action back or break open the gun ...so everyone looking my direction knows its empty and safe. I carry it open / or locked open ...to and from the club house and the range. No shells in the gun / or magazine ...the shells are in my pocket and not touching the gun.
There are too many people ...is close proximity of eachother ...to do it any other way. If you do not follow those rules - at my gun club --- someone will ask you to open your gun / unload it --- if you have rounds in the mag ...and hopefully politely / because some guys have never been around an organized shotgun club.
My local handgun / rifle range is even more restrictive ....you can't just walk thru the parking lot ...or around the range - with a rifle, handgun or shotgun - in your hand / even if the action is locked open....it has to be cased or holstered - or you will be stopped and challenged / politely hopefully.
Not everyone has a lot of experience ...or good habits on handling firearms ...but no better time to learn than now / before an accident happens. The same rules apply to me ...even though I have a concealed carry permit ...and have been shooting shotguns, rifles and handguns for over 50 yrs ...that apply to a newbie handling his or her first weapon - no exceptions....and sometimes the older guys are the worst offenders...unfortunately ! We all need to be careful ...and safe !