Re: whats a better round 338 ultra mag or 300 ultra mag?
Keep your 300 and 338 Ultra's....
I shot my 6x6 Bull Elk with slight hold over with standard factory, 200grn, Winchester Ammo out of a standard Ruger M77, stainless 338 Winchester Mag.
In the right shoulder...bulging to exit, just under the hide on the left shoulder: 550 yards!
Keep your Ultra's and good luck finding a box of ammo [$50+++], if you can even find them at a deep woods sporting goods shop...