Re: 300 Win vs. 300 WSM - Factory Rifles
I'll also throw in my vote for the Remington 700. This is a great action and can be made even better with a little work. I'd love to have an XCR myself, the coating looks to be great for foul weather hunting and the Limbsaver pad would should really help with magnum recoil.
As for caliber, the XCR also offers you another choice that may be a better long range caliber, the 300 Ultra Mag. So to break it down:
WSM: short action = lighter gun.
WM: old standby with ammo available everywhere (WSM is catching up though)
Ultra: flat trajectory, highest energy,
Any of these will be more than enough for most western elk.