I've only been a couple times so take my limited experience with a grain of salt. When inquiring on caliber/chambering, the outfitter asked what I had in the stable already as he preferred comfort/familiarity with something over a larger chambering just for the occasion. At the time, I had 30.06, 300wsm, 338 Win and 35 Whelen - "hey, any of those are perfect but bring the Whelen – I haven't had a hunter shoot a bear with that chambering yet".

His take is way too many guys show up with new rifles and are relatively over-gunned and under-experienced with it/them.
And Phil Shoemaker has reinforced this same thing here for an eternity.

One other note - the gentleman I hunted with is a well-known sheep hunter and his clients have taken several good bears on sheep hunts with .270's - and with zero drama. That's not to suggest it's ideal, just that folks that haven't done it before think it has to be a howitzer to be effective. I'd definitely begin with .30 cal as the starting flavor.

[Linked Image from i.imgur.com]

WWP53D