Our High School mascot is the Bear, (Go Bears!) and we have two mounted grizzly bears in our high school. One in the gymnasium, one in the lobby near the principal's office. Both were donated after the hunter passed away and his wife was cleaning out the house.
Near the base of each mount, there is a little placard telling about the location and the kill, the date, and the rifle used. One was killed with a 7mm Remington Magnum, one was killed with a .300 Winchester Magnum. Both hunts were guided hunts, so I presume that the outfitter had a back-up gun that he was both comfortable and capable with.
I don't think that I'd go after a grizzly bear with a .30-30, but plenty have been killed with them. I think that it's very interesting that the Alaskan CoPilot rifle
is available in .45-70, as is the Marlin Guide Gun
. I believe that any firearm above .30-06 should be capable of taking a grizzly bear, as long as your guide has a heavy thumper to help keep you safe.