Alaska Master Guide Phil Shoemaker I’m guessing has witnessed more Brown/ Grizzly kills than anyone on the planet. He sides with Alaska F&G recommendation to use a 30-06. The smallest cartridge any of his clients has used was a .270 Win shooting Partitions, 2 shots in the lungs bear died quick. He did state to hunt with whatever gun you shoot the best so if a client showed up with a .243 shooting Partitions or any deep penetrating bullet he would have no problem. The bear he killed with a 9mm handgun was in self defense of his fishing clients on a river he fished for 30 years with no issues. For a self defense bear handgun he recommended something smaller you can shoot fast and accurate. I’ve never hunted bear in Alaska just find his advice interesting and wanted to pass it on. Phil does carry a 458 Win as his bear guide backup.
Guides don’t seem to get a lot of love on this subject apparently.