I carry a Marlin Guide Gun for protection/back up when guiding or packing in Grizzly country. I have never had to shoot one in self defense, but I feel very comfortable doing so should the need arise. If I was hunting grizzly I would carry my 30-06, as it is my favourite bolt gun. It also gives me a little more range. The 300 H&H would be perfectly capable of killing a Grizzly, and I suppose it would offer the same advantage over the Guide Gun which my 30-06 does. H4831 is right, grizzlies havn't changed since the .303 was king of the Canadian bush. Make a good shot with a properly constructed bullet from a 300 H&H and he's dead.