As stated, 12 guage pump with slug is probably the most common bear protection in Alaska for grizzlys/browns.
I'd be less confident with a single shot but in most realistic defense scenarios (bear unseen in brush at close range until it attacks) you aren't going to have time for many shots anyway.
If it is all you have, use the slug and practice hitting quickly (<2 seconds)from however you usually carry it.
I'd recommend upgrading to a pump though. Lots of other uses for them too.
Para Bellum,
.44 Mag is a little light, if you are going to be carrying a rifle anyway. You're better off with a Garrett or Buffalo Bore-level .45 Colt or bigger.
I'd be less confident with a single shot but in most realistic defense scenarios (bear unseen in brush at close range until it attacks) you aren't going to have time for many shots anyway.
If it is all you have, use the slug and practice hitting quickly (<2 seconds)from however you usually carry it.
I'd recommend upgrading to a pump though. Lots of other uses for them too.
Para Bellum,
.44 Mag is a little light, if you are going to be carrying a rifle anyway. You're better off with a Garrett or Buffalo Bore-level .45 Colt or bigger.