NOMERCY,
If it were me, I'd go along with CRITTERGETTER on this one. Federal "Light Magnum" with the Nosler 180 grain Partition would be the first factory ammo I'd grab. I'd like to make two seggestions. When you buy your ammo, buy at least three boxes and check to be sure they're all the same lot number. This will insure they all shoot the same and give you enough ammo for your hunt and to zero the rifle with. The second suggestion is to contact your guide and get his opinion on the best distance at which to zero your rifle at. He'll have all the info you need. Good luck. Let us know how it goes.