Just though I would throw in my 2 pesos here:
I am just having a Weatherby Accumark .30-378 finished myself for long range elk. I chose to go with a Zeiss Conquest 6.5-20 with Kenton turret, zeroed at 300, SHOULD be good to 1000.
Currently best load is 180gr TTSX @ 3360fps and best group is .287 @ 100.
I have to admit I am cheating a little on this one, I roll my own normally but have been swamped with work (and have never worked up loads or a rifle for this range), paid a local smith to lap and mount scope/level/turret and work up load. My boss has the exact same rifle but with the Thompson Long Range scope
and the same smith does all the work for him.
Cannot speak highly enough about Les, he is a member here and does excellent work.