Most people will grant that the .30-06 is suitable for taking whitetail deer, mule deer, pronghorn antelope, sheep, mountain goats, elk, moose, and black bear, provided you select appropriate weight and structured bullets for each species (lighter weight and more rapidly expanding bullets on lighter game, heavier weight and more solidly constructed bullets on larger game). The .30-06, no doubt, has also been used successfully to take grizzly and brown bear, but most people will advise a substantial step upwards in power to hunt these dangerous bears which can kill you if you do not solidly dispatch them. In my opinion, and I'm no expert just read a lot, the .30-06 is one of the best starter big game rifles because of its obvious versatility. If you become an avid big game hunter, you may choose to acquire additional rifles optimized for particular species -- for example a .25-06 for pronghorn antelope. The .30-06 can then fill the role of a backup rifle to these more specialized rifles. Others see no particular pleasure in having a number of rifles and are satisfied with one general purpose rifle -- for all but the dangerous bears the .30-06 fills that category pretty well.