I used to live in Alaska and of the ones you mentioned the .338 and 375 will be the easiest to find ammunition for. If it were me I would get the .375 and load it with 270 gr. Triple Shocks loaded to about 2750 fps. It will unzip any bear on the planet.

**The same could probably be said as to availability to ammo in Africa as well..while I agree with the use of the .375 for Alaska--that whole Africa thing has me still going a bit bigger--but hey, that's the cool part of our sport.. so many guns, so little time..

Ripp