RE: 300 Ultra Mag for Brown Bear
Now I have never hunted bears, but I know one thing for certain. Listen to your guide. Sure, we have all read the articles of that one hunt that somebody had, and the .300 was good. And we have seen the TV programs too. What is not being taken into consideration here is that you guide knows where he is taking you, and I am pretty sure it is not the same place you read about, or saw on TV. Might be close, but still different. It is quite possible, if he is a really good guide, that he has his "I keep this place secret spot" where he sees lots of BIG bears. He has to figure, if he can put you on a bigger than normal bear, then, his tip, and referrals will be better.
Bears, just like every other critter are going to vary by size quiet a bit based on where they live. Their diet may have some similarities it will make a difference. Even just 10-15 miles down the road. Higher elevation better supply of fish...etc.
Take the advice of the guide on this one. He knows what is out in "HIS" part of the woods.
And, for what it's worth.... I am jealous as hell that you get to hunt up there.