300
I have shot a charging griz it is not as easy as some guys make it out to be by the time I fumbled around it was at seven paces in front of me when he fell i shot him with a 300 mag with a 200 gr partition when i was out moose hunting I hit him in the throat and broke his neck but he still managed to take a few extra steps steps that made me crap my pants I also had a friend out hunting that shot a griz with his 30-06 180 gr bear claws it took six shots in the boiler room to make him go down he was 8'3 and his skull was 24" they are very unpredictable they will do almost the complete opposite of what you expect that is my experience anyway.so all in all take the gun you are most comfortable with it will pay of in the end.
I have shot a charging griz it is not as easy as some guys make it out to be by the time I fumbled around it was at seven paces in front of me when he fell i shot him with a 300 mag with a 200 gr partition when i was out moose hunting I hit him in the throat and broke his neck but he still managed to take a few extra steps steps that made me crap my pants I also had a friend out hunting that shot a griz with his 30-06 180 gr bear claws it took six shots in the boiler room to make him go down he was 8'3 and his skull was 24" they are very unpredictable they will do almost the complete opposite of what you expect that is my experience anyway.so all in all take the gun you are most comfortable with it will pay of in the end.