I use the same rifle (Vanguard in .300 Wby) for elk. It's topped by a Leupold Vari-X III 3-9x, which I consider the maximum for elk. There are times I've considered pulling the 1.5-5x Vari-X III from my .375 H&H and putting it on the Vanguard, simply for the lower end magnification.

Having a few seasons behind it now, I think a better combination would have been a 2-7x, rather than the 3-9x.