Never shot a .338 Remington Ultra-Mag, but my pre-'64 Winchester Model 70 "Alaskan" (std. 26" barrel) in .338 Win. Mag. is ALL the "rifle" I wanna shoot... especially off the bench-rest.
My handloads... a 210 grain Nosler Partition bullet @ 3020 fps... is more than "enough rifle" for anything that lives in the New World and, even with a 10½ lb. rifle, it gives all the recoil I can "comfortably" handle. No one shoots very well with "flinch-itis"!
Jus' my 2¢ worth... other's opinions may differ.
Strength & Honor...
Ron T.