I hear this ALL the time, I live in grizzly country, worked in AK on the west coast fish guiding for years, been woofed ,charged, investigated, smelled thru a wall tent in the middle of the night. An all out attack last 3 seconds from start to finish. So you have 1.5 seconds to ID your target and get off a killing shot, bleeding out is chewing on you as he a or she is do it. And as the bears range grows and it will and is. There's going to be more and more in counters . Best is to hunt in pairs, if someone gets something down,Everyone pitches in till its been done, keep a clean camp, and be bear aware. The last thing you want to do is shoot. Beleave me on this, you haven't got a clue as to how fast it happens. If your seeing grizz sign get out of there stay away from kill sights,.I'll be using a 50 o r 54.
I totally agree with Mtman! Having a good bit of experence from living in Alaska for many years and being around big bears. When I first moved there at 19 I carried a 357 with me while fishing or in the bush. A fishing buddy ask me why I carried it. I told him for bear....He told me that most likley it would'nt do me any good...It would just make one mad!! This as he carried a pump shotgun loaded with slug and buck. After considerable though and a couple of years I too started carring a pump gun!
I would go with what you shoot well in either a .50 or .54, I would tend to lean towards the .54 as that is my ball of choice. BUT I would add I would shoot well built bullets! 3 Trees