There is no right answer to this question. Just to many different cartridge's that fill the bill wonderfully. But I do believe the starting point is 6.5mm cartidges because of better bullet's for larger game. I am certain the 24 and 25 cal will work well on even big elk. But then the #2 world record Grizzly Bear was killed with a 22 RF Long. I would not suggest trying that!
