My cousin, now deceased, lived in several of the western states for many years. He killed 22 elk, almost all bulls other than a few cows on cow tags, using his pre-'64 Winchester 70 Featherweight in .308 Win.
He did not reload. I asked him once about what ammo he used? He said, "Winchester, Remington, whatever was on sale at the gun store, so long as it was 180 grains." He had no trouble putting those elk on the ground. (I don't know how many Mule deer, he killed but he also killed a couple of Black bears, and one Idaho Shiras bull moose, same rifle, same load.)
I know he never took any of those 600-800 yards shots... but he was an excellent hunter, stayed in good shape, and practiced shooting for accuracy. Got closer to the elk. Meat in his freezer.
Good luck on your hunt.
L.W.
