Welcome from Wisconsin. Congrats on the build. Start running triathalons and serious weight training if you are going to be humping that Eliminator 3 on top of your 308AR through those Montana mountains. At 3.3 pounds, that scope is a load! I had an earlier eliminator and sold it as it was too heavy and destroyed the balance of my AR10T carbine, and I found with practice with a simple BDC reticle I could do as well.
Out to 600 yards you will be fine with that 18 inch barrel, especially if it is a 1x10 twist, and you are using bullets in the 168-175 grain range.
With all due respect I would take the time to practice distance shooting without electronic assistance, as batteries fail at the wrong time. Having the built in laser range finder is nice, though, I miss that.