To the OP, with the greatest of respect, these bear and ballistics threads of yours suggest a mindset not really suited to conditions where Brown Bears may constitute a threat to you. Again, no disrespect intended, but you do not seem constitutionally suited to the situational awareness and response type required in high threat situations. Any well constructed slug or bonded core/partition type bullet from 250 grs upward delivered with a terminal velocity of @1300 fps + and center mass shot placement will suit your ballistic needs. You need to focus on 1) avoidance, 2) egress when in proximity and 3) ability to put firearm on target as rapidly as possible in the event 1 and 2 don't work out. Any of the three or four (counting 454 and greater caliber revolvers) of the firearms you mention will work effectively in the event 3 becomes necessary, but you really seem to need to buck up, get some training in 1 - 3 and become confident about your ability, if absolutely necessary, to do 3 with whichever forearm you choose. Again, with the greatest of respect to you for seeking knowledge, right now, your mindset is a much bigger issue than your firearms choice. I wish you the best in your travels and urge you to focus on 1 and 2 as much as 3 and to train for 3 not just mechanically, but mentally.