My grandfather hunted his entire life with just 3 center fire rifles; 22-250, 30-06 and 375 H&H. He always said if you need something more than an '06, you need to step up to the .375 or .416.
My father is of similar thinking, but his primary big game rifles started with a .243 and 308 Winchester. The .308 he used for everything up to moose and grizzly. He later got interested in the .338 Federal and now uses it almost exclusively for anything from mule deer through a coastal brown bear. I don't think there is a whole lot of difference between a .338 Federal with 210 Partitions and a 30-06 souped-up with 200 grain Partitions, so I believe nothing in North America is out of bounds. Pop also used his .338 Federal on Asian water buffalo, so even the big bovines are within reason, with proper bullets and prudent marksmanship.
