Quilly,
I've seen guides suggest 33 cal and bigger too, but i always figured that was crazy!! I've seen guys hunting with 348 winchesters! Bigger than 33 cal, but is it better than a 7 Rem. mag??????
At one time i hunted with 338's a lot, (and shot, deer, brown bear, moose, caribou, ect..) but after extensive bullet testing i saw for my self that a 7 mag with 175 NP's will out penetrate most all the big bores (includeing the 375 H&H, and .458 win Mag.) with std. expanding bullets. I found hunting with a 7 Rem. mag. to be just as effective, as long as i used the "proper bullet" for the game hunted. On big bears shot placement with lots of penetration is what your after!!
In my experence, for anything in the U.S. the 7 mag. and ALSO the 30-06 "with proper bullets" is more than enough gun, even for big bears!! Of course, you have to be able to "shoot well" with what ever you carry!!
Drilling Man