I doubt there’s much difference, group wise. Moose are pretty hard to miss. I would shoot the heavier bullet. Remember, one inch at 100 was the standard forever, for good reason.
It will work fine for Moose. We’ve taken two very large bodied Shiras with a 30-06 and 180 ttsx’s (350 yards and 30 feet) and I was with my buddy when he took an average sized AK moose with 7mmRM and 150 core-lokts [150 ish yards). Myself, I’d lean to TTSX’s or heavy high weight retention bonded designs like the swift A-frame just in case of brown bear trouble. If it’s just grizz country, partitions, AB’s or heavy cup and core etc. would all be fine imo. If the guide is carrying a rifle, then no bear bullet choice worries.
Moose are big and even with a perfect heart/lung shot can take a while to slow down and fall. They are not particularly tough so much as big. I‘d be prepared to keep shooting until he falls. If he runs and water is near it can be a bad deal.
It will work fine. Pick a decent bullet and stick it where it belongs. I have taken 4 A-Y moose. Two with a .338 and 2 with a .375 Ruger. I always carry more than enough gun being a bit of a rifle looney.
I would put one in the boiler room, watch his reaction, and if sure of your shot, he will likely stand there 30 seconds and tip over. Sometimes additional shots , especially if they hit bone cause them to move or run.
Pick whatever you would use for elk and you'll be well armed. Lots of moose get taken with 270, 30-06 and 7mm RM , the 280 is in the same class as those. A friend of mine has used a 280 for years and taken a lot of moose including some big bulls. Usually uses the 160 gr Partition.
my two cents. Yes I have a custom built 7 saum. It shoots anything I try really well. I choose the 160 accubond. In the last two years it has killed a 343 inc bull elk at twenty yards, a whitetail at 595 yards, two bears at 400 +, a 300 inch bull elk at 150 yards, a caribou at 595, and my moose at at 310 yards. All one shot. Everything I shot at, that bullet hit right where I wanted it to hit. I would never go beyond 600 yards with accubond because i am not sure the energy on contact that the bullet will do what it is supposed to. But it will go where I aim. Anything from a .280 up is deadly. I was told on my moose to aim back from the front shoulder. I aimed six inches back and wasted zero meat. If I could figure ou how to get a video uploaded, i could share my moose kill. 300 yards one shot. he fold over backwards. I personally think it is how confortable you are with your rifle because then you will shoot well. Shoot, shoot ,shoot and shoot some more to know your rifle. Anyway my two cents
I would say so. I killed a Canadian moose last year with a 150gr Hornady CX from my 7mm RM. 30 yard shot through both lungs. I would expect similar results from your 280.
.280 should do the trick, my .270 did just fine in the Yukon. Shot him quartering to with 140g Swift A Frame and pulled the bullet out just penetrating the rear ham. Dropped him like the Hammer of Thor.