Dewey,
A couple of years ago I semi-decided the cut-off for an appreciable and consistent difference in "killing power" (however that is defined) is around .35 caliber.
Bill Steigers at Bitterroot used to say this all the time, too....drilled it into my head for years.
A good friend who guided for 10 or 11 years on elk, and saw 4-6 BIG bulls put down every year in those years, feels that 338" and above, especially when coupled with magnum velocities, is where he saw a greater "visual impact" on those big bulls. He liked that because when watching an animal being hit by a client through the spotter or binoculars it was easier to tell how/where/if the elk was hit. He thought the 340 Wby was the cream of the crop in this regard, and also said the most dramatic "bang flop" on a big bull he ever witnessed was with a 378 Wby.
But he also didn't believe those rounds necessarily "killed quicker" (except perhaps the 378), but definitely gave a better visual. Course the bulk of the hunters he was guiding were out-of-staters packing various magnums, so "killiing quicker" is a relative thing.
For his own elk hunting he used a 270, and currently a 260.
All of the above in grizzly country...
