I carry my Mossy 500 with bearspray on the hip and 2 extra full loads.
I use 2 ¾” , 3”, 3”, 3” , 2 ¾” slugs.
I found that I get a better first shot with the 2 ¾” shot than the 3” and having the 2 ¾” at the rear helps prevent my follower from jamming, also if I am using that round the bear is on top of me.
Recoil from slugs can e painful and you really need to practice. Everytime I go out in the field I take some extra rounds with me and practice. I also make sure that I fire the gun before going out as I have had two failures, (load and to fire) If you don’t shoot it, you won’t know if it works.
If you can’t take extra ammo or will get a chance to shoot it, get some snap caps to check that it cycles and by placing a tiny piece of tape on the snap cap primer you can check that it is being hit. Also practice with birdshot and 2 ¾” slugs.
Plus cycle your carry ammo regularly, so it stays fresh.