Paladin: I have a 625, 45 Colt caliber Mountain Gun. I load it with 7.9 grs of W 231 behind SAECO's #458, 250 gr bullet. There's nothing magical about the 7.9 grs: it's what the #13 rotor for the RCBS Little Dandy powder measure throws. #12 gives 7.2 grs, too little, and #14 gives 8.6 grs, too much. My bullets are cast soft: 1 part linotype to 2 parts lead. If I were carrying it in bear country, I'd cast them of straight lino for more penetration.
I have an El Paso Saddlery Tom Threepersons holster for it; as I live in El Paso, I got it off the shelf when I went down to the shop. Mountain gun or no, that thing is heavy and worn on your belt, it will take your pants plumb off in no time.
Possibly a better bear gun is one of the Scandium 44 mags; I understand they're real big amongst Alaskan guides. However a handgun is only a last ditch gun against bears. When I was stationed in Alaska, I carried a 458 Winchester for a while when we went out berry picking. It got heavy, so I went to a Remington 760 pump carbine (18 inch barrel) in 30-06. Loaded with 220s it's pretty good in case that guy picking berries on the other side of the bush turns out to be a bear. Probably not too feasable to carry a rifle in a National Park, however.