I would think that shooting an elk at 600 yds with a 243 would be akin to shooting one at 100 yards with a 22 lr.
could be done,but why would you?
seems someone who can afford to shoot tens and tens of elk should be able to afford a more suitable rifle.
Again, he's killed scores, you've killed what?
The rifle that you shoot well with a bullet that kills cleanly is the appropriate rifle. No?