.338 Lapua . It wouldn't hurt to buy the best glass you could get , Nightforce scope and a good rangefinder that can go the distance. I would start trying to get Lapua brass and SMK bullets awhile in the 300gr catagory. $$$$$$ Let us know how it shoots.
I love my leica 1600 crf rangefinder! I would also invest in a nightforce 5.5-22x56, ballistic app for iphone and a kestrel pocket weather station. Good Luck! Let us know how it shoots. I should be receiving my 388 lapua this week sometime too!
Good choice, DRbill. Whichever range finder you choose, make sure it automatically makes ajustments for ranges when shooting at severe angles. It should give you actual range, a visual angle, a printout of the angle in degrees, and an adjusted distance for the angle of the shot.