I'd leave the .300 RUM home altogether. The .280 will do it all. Take an extra scope, already in mounts and sighted in. Save weight, space, and aggravation. KISS principle.
Pretty much anything in ammo that is accurate and weights around 140 -160 will do it all in the .280 too. Premiums not needed, but won't hurt. IIRC Jack O'Conner took a trainload of stuff all over the world with .270 and 130 to 150 gr. bullets, I think before Partitions even came along - or maybe not.
I do have a couple 10 poundish rifles - a Ruger 77 in .338WM which I use for moose hunting in my local area where I won't be hiking more than a few miles a day, at most, and a heavy barreled M98 in '06 that I use up here for hunting caribou, where I'm seldom more than a couple hundred yards from the snow machine, ATV, or boat.
If I'm doing anything strenuous, or packing iron for a long time, I'm carry something under 8 lbs or so - either a .260 Rem 725, 700 .243, carbine style RU77 in '06, or a '94 in .30-30. Those too have worked well over the last 40 years or so, from moose on down. No brown/griz tho. Never had the desire or occasion.
It ain't what you hit 'em with.... But don't let me stop you from playing with a favorite toy!
Enjoy your hunt!