I've been picking up some strange problems with my 300RUM reloads. would appreciate any help. Here are the details: Foster CO-Ax press Foster dies (FL sizing die) Rem brass (twice fired) 220gr SMK bullet CCI mag primer Local powder (South African) I've sorted the cases by uniform case thickness and weight. All cases have been trimmed to uniform thickness, just below max length. Problem: The case won't chamber 100%. The case slides forward into the chamber until it seems that the shoulder of the case or neck enters the neck / shoulder part of the chambering then there's trouble. This never happens with new unfired cases. It seems to me that there is a doughnut effect at the junction between the case body and shoulder. This does not happen with every case, probably 1 in 5 cases. Sometimes this doughnut is not visible to the eye. (it is also quite possible the this may not be the problem and that I'm missing something else). Can anybody shed some light oin what's happening ? Is it possible on seating the bullet that the bullet is pushing down on the neck thus deforming the shoulder ?