I lived and hunted in Alaska. The 06, 300 Win Mag, 338 Win Mag, and the 375 H and H were the most popular and used.
300 Win Mag is more than adequate for the big bears.
I've seen the large bears taken with the 06, 7 Rem Mag, and the 270.
Shot placement is a big part of it as well.
On any game animal.

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