My own view is that modern shotguns made with modern steels are pretty difficult to damage. Weld up the muzzle and you will probably blow the end off your gun. Some yankie u toob vids are of people putting 20 bore carts in a 12 bore (rem pump I think) and couldn't do any damage to it all. I have been using slugs and any number of improvised projectiles including hand grenades, (in the middle east) and not yet managed to blow up a gun. We bruised a few shoulders though!
Whilst I wouldn't recommend doing any of the silly things that we did in the desert to anyone else, I also wouldn't tell them not to do it either provided that they don't put others at risk.