Try some gunshops, gunshows, Gunbroker.com, Auction Arms, and GunsAmerica.
You're posting at a place where people mostly want guns, not want to get rid of them.
The 280 suffers because it's surrounded by the 270, 30-06, and the 7mm Rem Mag which are also good cartridges. Few manufactueres are making guns in 280 any more. There's no 280 Ammo at Walmart. You could rebarrel a 270 or 30-06 but that would cost more then finding a used one.
If you look for one try to get it with a 3.6" magazine so you can shoot the excellent low drag bullets which exist. Rem 700's do. The SAAMI length of the 280 is the same as a 30-06 (3.34") which is not conducive to long ranage shooting.
Only you can decide what's suitable for you and your environment . Thats's true for the cartridge, and accessories. What's usually called a Mountain Rifle. is just a little lighter and shorter than a classic BDL rifle. The term says little about accuracy or quality or even if it's actually desiraable for use in mountains.
