I haven't done any of this so not trying to sound like a know it all so I'm just explaining it as I understand it
Back info: When you neck down brass you thicken the neck by forcing the same amount of brass into less space. Ideally after you neck down it would be best to turn to necks to bring them back to the right thickness so there is no chambering or neck tension issues.
My question: When you neck up you must be thinning the necks, and you can't do the opposite of neck turning and add brass.
Does this kill the life of the brass? Do the necks or shoulders split real quick or anything?
This would be for .270 > 30-06 specifically.