Skeet and Sporting Clays are different game, but loading the mag between pairs is not a problem.
Long story on the barrel thing. Short version. I show up, shoot. At the end of day one I get told my scores are null and void as I was using a "tracking device". Further told that if I don't change gun's my scores will continues to not be included.
I return to my hotel, read the rules and contact a few Cats more knowledgeable than me. "Tracking Device" in under the ammunition section of the rules and refers to tracking wads and or luminescent element in the ejecta, not anything to to with sight systems.
Further. Red Dots are mentioned within FITASC rules (not sporting) so they are ok in Sporting.
Next day I shoot (for no score) and at the next to the last station a guy rolls up and tells me my scores have been reinstated.
If you feel like it listen to minute 17-20 of this podcast. The NSCA lead dog says a clean-up of the rules are needed to eliminate Assault Shotguns and a 24" rules should fix it. (it was already 26" in FITASC)
https://podcasts.apple.com/us/podcas...=1000552803399
Happy to answer any more questions!