I agree to an extent. It depends on whether or not the guy doesn't shoot well because he just doesn't shoot well, or if he is being distracted by the recoil of the rifle he's shooting.
For example, I've seen guys that shoot a .243 a lot better than they shoot a 7mm Rem Mag, but that's because they have no mental distractions or fear of recoil from the .243, like they do the 7RM.
But if we're talking about two cartridges that recoil very similarly, like a .30-06 and a 7mm Rem Mag, then if you can't shoot one, you won't be able to shoot the other, either.
