A short while back I posted a thread about a batch of Sierra Match King bullets varying by .030" base to ogive. I would suspect the bullets before the calipers.
I would agree with this.
Step one would be to measure and sort a bunch of bullets with something like a Sinclair Nut. Have all bullet base to ogive measurements equal or within 0.001 of each other. Then do your normal bullet seating measurement operation. If, after seating, the COALs are consistent you know it's the bullets, if not, it's something to do with your seating operation. I really don't think it has anything to do with the brass.
