You might get the barrel hot enough that you wouldn't want to touch it, but you aren't going to damage it. Shotguns are pretty 'low intensity' compared to rifles, burning out a barrel isn't a problem in a shotgun- heck, it STARTED as a smoothbore. I can't see a sustained fire situation developing where it would be necessary to shoot 50 rounds as fast as possible (Awerbuck's 'Rolling Thunder' drill is only 15 rounds per shooter) but you won't hurt the barrel if you do it.
Learn to load at the shoulder and you won't have to touch the barrel, hot or not. Get on the list for the Awerbuck video in the Lending Library, that will show you how.
lpl/nc