Don't know much about the 280, but I have a remington 700 mountain rifle ina 35 whelen, and it's a perfect factory rifle for elk... light weight, accurate and aesthetically good looking. Good buy, and good luck on finding a good load. I'd hit up the AR forum for loads if yu can't find help here.
I have the same rifle in .280 and have used it on elk. I killed one elk with it before I got my .338 WinMag. I can tell you what NOT to use. Don't use Winchester Supreme Silvertips. They were around 160g. These were different than the Ballistic Silvertips that are out there now. All I found was fragments. It was at point blank range, but still shouldn't disintegrate. Elk was still dead but I wouldn't take a chance with them again. I have also used Winchester Failsafes on mule deer. They punch through but don't expand as much as I'd like. My recommendation is to stay with the heavy-for-caliber bullets...around 160g. Good heavy construction. I like Nosler Partitions but there are plenty of good bullets out there. I have heard Barnes makes a good bullet but don't have any first hand experience with them. I took a quick look through Cabela's ammo selection and sadly, there are not a lot of heavy game rounds available for the .280. Most of what's available are 140g and 150g deer rounds. It's a shame Remington doesn't sell a .280 in their Safari grade line. It would have a Swift A-frame bullet which would be fine for elk. The 700 Mtn Rifle is a great gun for elk hunting. Easy to carry and handy. Good luck with it.
As I sit and glass, which is common for hunters out west, I have sort of quickly discovered something I never learned when I was younger.
In my youth I had enthusiasm and spirit. In my middle to advancing years I have creaky knees, arthritis, and I tire more easily than I used to. Where I used to sit on the cold hard ground I now look for that soft spot to sooth my tired muscles. That leads me to my tip.
Carry your soft spot with you!
In my pack I carry an air filled, ultralight, camping pad....