Just out of curiosity, how many guys do you know personally who had to shoot a grizz, brown or polar bear hunting moose or anything else besides bear, in self defense while on a guided hunt. I have hunted and guided in big bear country all my life, I never saw it, nor do I personally know anyone who guides or hunts bear country that has. Bear defense gets talked about a lot, it doesn't happen very often. The only bears I have ever shot in self defense were bears we were actually hunting.Ypur 28 Nosler will work fine but I would look at 30 or338 cal instead. The Alaska Yukon Moose is the big boy on the block approaching 2000 pounds. How ever it is not the Moosw you need to worry about it is his neighbors up there. What ever you do don't shoot your Moose in the hump all it is,is bones above the spine. Good luck. Also I would use a Barnes or Hammer bullet if it were me.
So just because you have never heard or seen it happen it can not. What I was trying to say was it could and has so be prepared. The old Boy Scout motto stands true. Be prepared for the worst and it most likely will not happen. If you are not and it does it is to late. Beside if it is no risk why do Alaskan Guides prefer larger cal rifles. It is becoming a real threat here in Alberta and we don't have Alaska's Griz population.