For 1: The people that are shooting long range matchest are full length sizing there cases every time. 2. I would be throwing those cases in the recycling bend sometime back. You are screwing up you chamber. Nothing said about annealing the cases. (That doesn't have much to do with case separations,but) I would say either your dies aren't adjusted correctly or your head space is off. Past time to go to a gunsmith and have it checked out. With what you are showing, it would appear that you are not checking for base separation after firing the cases. You can get a larger paper clip and sharpen one end. Put a very short 90dgr turn on it and straighten out the rest of the paper clip. put it inside each case to the base and move up and down about 1/4" around the inside of the base. It your point catches moving around the case base inside it's showing starting head separation. Time to recycle that case.