What exactly is 'ballistic balance'? Start with what you want a bullet to accomplish and the range you need the bullet to do that. If being able to hit and kill at 700 yards is the end point, 'balance' is completely different than in the same scenario at 300 yards. The former 210 grains, the latter 165, would be the 'balance' point for me. It must be a given that the rifle shoots both well enough.
It all starts with hitting; followed by 'what' and 'where'. Fortunately the .30 cal is wealthy in that regard.
By ballistic balance, I'm talking of the point where the minimum windage deflection occurs. Elevation is easy to dial in as it's basically gravity and time. Windage however is harder to compensate as wind is not the same at all points out to a long distance. In order to minimize windage error, it's best to use a bullet which has the least deflection for the velocity capabilities of the cartridge.
For a given cartridge, there is an equilibrium point whereby the heavier bullet with higher BC will have more windage deflection than a lighter bullet with lower BC because the heavy bullet will travel at lower velocity and due to longer time. For 300 RUM, from class I've done since the initial post, it looks like 225 gr has the least deflection at 700yds.
