Also, as someone mentioned before, experienced Alaskan guide Phil Shoemaker recommends the .357 Magnum loaded with 180 grain hard casts for grizzlies.
Read one of his articles last night in Handloader seems like he totes a pump action shotgun full of Brenneke slugs for said purpose. I know a guy that carries a 357 when he bowhunts Wyoming grizzly country and has had one bear problem and he really hoped he didn't have to use it. Proper shot placement on an animal that is pumped full of adrenaline and hell bent on your destruction that incidentally runs 35 miles an hour good luck and all with proper shot placement.