On most 3 die sets, the second, de-priming die also should be adjusted to slightly expand the case mouth at the same time as de-priming. No point going back and doing it as an extra step. When you seat your bullets, make sure you adjust your seating die to remove the slight "bell" you put in your case mouth when you de-primed. When using 296 / 110 powder, at least in a .44mag, you need a decent crimp for proper powder burn. I assume it would be the same with a .460. As you look up data for the .460, you may find a more suitable powder that does not require a crimp, as bullets moving forward under recoil is not an issue in a single shot, as it would be in a revolver.
Its always a good idea to follow reliable reloading data from manufacturers, or in loading manuals when it comes to primer selection. I do not reload for the .460, but you may find it requires a rifle primer due to its operating pressure, so, again, check. usually I start out loading to standard OAL, then experiment with seating length if I feel accuracy could be better. You definitely do not want the bullet jammed into the lands, or seated to deep, as each can raise pressures.
Larry