I have two older Ruger 77 MKI's chambered for .280 Remington. one with the factory sporter weight barrel, the other with the (sorta rare) factory Varmint weight barrel.
I think they are very close to ideal for a Long Range Hunter, each depending on whether one is stalking or stationary.
I think that the .280 is superior to the .30-'06 at all realistic distances, with both better retained terminal energy out far, and recoil that's somewhat less than the '06, which is what I (and the US Government back around the start of the 20th century) deem to be the practical upper recoil limit the average soldier could tolerate in a sustained manner. Bore life should outlast the magnums as well.
I believe the customary 1:9" rifling should stabilize bullets of up to 165/168gr; and that heavier bullets are unnecessary for good terminal performance, as well as defeating the basic premise of keeping recoil down to a level that promotes adequate practice and familiarity with a serious hunting rifle under numerous conditions. Better Hunters don't just shoot their primary rifles during hunting season, they keep in practice all year long.
I believe the Nosler 150gr hunting bullets might conceivably remain supersonic out to 1000yd, and that their heavier brethren should remove such doubts. Hornady 139gr SST Superformance loads are outstanding closer in. Remington 140gr Core-Lokt Express are very good bonded bullet loads as well.
IMHO, the .280 could also serve well as a LR Target or Tactical chambering, too.
Greg