The reason larger-bore rifles are usually used on brown bear (or other large animals) is not because they necessarily kill "better" but because of heavy bone--especially on a bear coming toward you. A heavier bullet has some advantage in getting through heavy bone and staying on course, though not as much as a lot of people like to believe.
But a modern high-velocity rifle like a .270 or .30-06 kills just as quickly as a medium-bore rifle. I know this because I've seen a lot of animals bigger than deer shot with a wide variety of cartridges. Among them have been a number killed with black powder cartridges and lead bullets. The reason is that a high-velocity expanding bullet makes a big wound in the vitals--on average, bigger than the hole from a moderate-velocity medium-bore or a big-bore black powder rifle. And messing up the vitals is what kills animals, not the size of the hole in the barrel.
Elmer Keith went to Africa in 1958 with a .333 and really poor 300-grain bullets. They worked so poorly that he eventually started shooting even Thomson gazelles with solids. From that experience he concluded that ALL African game is incredibly tough. He wouldn't have had any problem killing any of his plains game, however, with a .30-06 and 180-grain Nosler Partitions--and Partitions had been on the market for a decade by then. But he refused to understand new technology.
If you prefer to believe in the magic of bigger bullets, why go ahead. Elmer did, and chased a bunch of dinky antelope over large portions of Africa.
Spot on, +1......
I got banned on another web site for a debate that happened on this site. That's a first
