I hunt a lot of places with Mountain Lions and one area with wolves. Never been attacked, I have been stalked by 1 bobcat (at least that I know of) and have had several coyotes respond to my calls.
I do not carry any other shells than my turkey loads. At self defense ranges they will be plenty adequate. If attacked I really doubt I would have time to unload my gun. fumble for a different shell, and reload. Its possible but if a Mountain Lion is staring at me I just don't think I am going to empty my gun.
Last year in Wis I had a neat encounter. It was a Tuesday and you only hunt Wednesday thru Sunday in Wis so I was scouting and didn't even have my gun with me. I was walking down a road and had heard a distant gobble. I got off the road and stood in the barrow pit and was waiting to hear him gobble again so I could see where he was headed. For some reason I looked behind me down the road and saw something coming. Figured it was a deer at first but the gate was wrong. Yote I thought and put my binos on it. It was a wolf! I sat down in the barrow pit and then remembered I had a camera in my vest. It came within 20 feet of me when it heard the camera clicking. Stood there for a minute and then headed into the brush.