I could use some help. I am going to have a custom rifle built and am having a hard time deciding which one. I live in Alaska and would like a rifle to hunt with and use as back up for grizzles/brown bear and possible use in Africa. I have narrowed it down to 338, 375, 404 or 416. I have read alot on each caliber but still can't decide. I would like to use the heaviest bullet available in each caliber i.e. 300 grain in 338, etc.

Thanks