Home Forums Hunting & Shooting Ask The Gunwriters concentricity problems caused by seating

I am increasing neck run-out mostly from bullet seating. Run-out is consistently around .002" from sizing and then jumps up another .003-4" from seating Barnes tsx using RCBS dies. In your experience, what is the most likely cause? I have always had more run-out created in the sizing process but not in this case. Thank you.