My dad and one of my hunting buddies carry there hunting loads in there 30/06 and then their 220 grain Power Point bear rounds in their pockets when hunting. It seems to keep them happy I don't point out the "4" 220's in there belt pouches are really going to be of no use in a close encounter with a grizz...
The key here is that if an individual is to carry more than one load at a time, those loads must A) shoot to the same point of aim within the range they are intended to be used, and B) serve a purpose that the primary load cannot fill.
Your Dad and his pals would be better served if the first round in the magazine was a bear load and medium game loads followed below it. If the opportunity for a shot at a deer occurs in thick cover, the 220 will kill the deer, but if they get a longish shot there's time to run the 220 through the action and load up a 150 or 165 gr bullet to reach out there. If they have a dangerous bear encounter, the heavy bullets will never be used if they are carried in a pocket. Within 25 yards, the heavy bullet load will shoot close enough to the primary load that no sight adjustment would be necessary, but if they were to consider a shot out to 50 yards, they had better know where that load prints when the rifle is zeroed for another.
I keep telling myself that I'm going to make it back to the Yukon for a Dall sheep hunt. If and when I do, I'll be packing my .375 Ultra, and I still have a few 260 gr Nosler BT's loaded for the adventure. Because I'd be in bear country, I'd also carry a 380 gr round as the first round out of the magazine, as I do at home. This is where it would be until I was ready to begin a stalk on a sheep.
At home it's the same, when I'm hunting the medium game loads are below the 380. The 380 will work on any big game should I need a fast close range shot so, the only need to change to the 260 is if the range exceeds 150 yards, and if it does, I have time to cycle the top round out of the rifle. The drop of the 380 at 300 yards is 22" when sited for 150 yards. A drop of 22" is a bit much to deal with when the range is unsure. The 260 drops only 9" at 300 when loaded to a moderate 2600 fps. At full speed (2850) the drop is 7.5" and I doubt I could make use of the difference at 300 yards. If I can get closer I do.
My small game load of a 270 gr Hornady or a 300 gr cast ahead of 18 grs of Unique makes a flat subdued bang when it fires. I have fired this load within sight of caribou, and they have not reacted, although I'm not sure if this would continue to be the case during a hunting season where a herd has been exposed to gun fire. While these loads are accurate and shoot to point of aim out to 100 yards; their purpose is to take small game at 25 yards which they do with no more violence than a HI-Speed .22 LR.
If I am moose hunting I would probably carry 300 gr TSX's, although the 260 gr AB's work as well for big deer. If I loaded the rifle with 300 gr TSX's the 380's would probably stay at home. The 300 TSX will deal with any truculent polar bear, so there would be no need for the heavy weight, and often, although not always, moose hunting occurs further inland where polar bear problems are less likely.
I'm sure this will cause some to question if I doubt that a 260 gr AB would kill a polar bear. Not at all, but in a close range defensive shooting the 380 is the only expanding bullet I tested that did not loose mass with close range hits. My criteria was that I would pass on any bullet that I could make fail when fired into the same test media at the same range. The 380 expanded to nearly an inch and the wound cavity was 2-4X that of any other bullet tested. For bear work, that's the bullet I want.