FYI, there is an ELR Forum:
ELR - Beyond 1000 Yards
Chances are you might have better luck there.
That being the case, you are going to need to provide a lot more information than what you started with if you would like any kind of a logical, rational, or educated reply.
What are you shooting at that range, 2 legs, 4 legs, or paper/steel?
Factory or Custom Built Rifle?
Factory or Handloaded Ammo?
Rifle Budget?
Ammo Budget?
What Does or Does Not Matter, Barrel Life, Recoil, etc?
Not trying to discourage you, but with a lead off post like that, makes me wonder if you are aware are of the demands of ELR shooting? I have seen plenty of shooters who thought ELR shooting was going to be cool, to only quickly end up frustrated, broke, and ultimately throw in the towel.
Do you have a very strong base for precision shooting, especially for shooting at distances of 600-1,000 yards? If not, please start there, because there are no short cuts for ELR, and trying to make it successfully without a very strong foundation there is usually a recipe for failure.
Please provide some more details, and I am sure you will get plenty of help.