Well,
To a certain extent, yes, that is an assumption one can make MOST of the time. When It can't be done is when the bullet types are completely different.
Two lead bullets are NOT necessarily similar enough to exchange data like that. Nose configuration, bullet design, ballistic coefficient all come into play then.
I can hear you say "WHAT? BC comes into play." In this way, how deep does the bullet go into the case? If the bullet is a "1R" type bullet where the nose has most of the weight then you might get away with using an OAL for another type of bullet. If you go from a standard type of SWC to a Keith design, yo can get away with it too because most of the bullet weight is designed to be outside the case. But turn those things around and you can have a bunch more in the case or up against the cylinder throat and viola, pressure goes up exponentially.
How much "set back" can a bullet have in the 460 before the pressure spikes in a real bad way? Don't know? Me either, but I'll bet you it happens just the same.
Nose shape, bullet depth in the case can change drastically with different bullets. If it were me, I would run the minimum load over a chronograph, see where I was and back it down until I lost the pressure signs.
If you don't have a chronograph, get one!
FWIW