I'll defer to those with far more expertise ref the bullet weight and velocity ranges. I've heard this point raised before and won't argue it certainly.

Woodleigh does make a 480gr Solid or Sn for the .458 and that might be just the ticket to solve the case capacity issue in the 458 Win.

Dugaboy1 and others... Does the 480gr Woodleigh with proper powder and load choice bring the .458 where it needs to be? Seems with the right choice of powder it should be able to hit 2100fps in a 24" barrel with that 480gr? Especially in the Ruger #1 with it not having the COAL limits of magazine guns.