big, I do not use the expander ball. I paid close attention when I set up the Redding die, in fact I have a second die for another rifle set up the same way. I know that the die can cause the case length to 'grow' by a few thousands before it actually bumps the shoulder. I witnessed that and kept adjusting my sizing die down ever so slightly until I saw the 1 to 1 1/2 thousandths of change in the case headspace. I'm starting to wonder if your comment, I think it was you, about chamber length could be on to something. I seriously need to measure the length of the chamber to see if this rifle has a short one. In order to do that I will need to order another tool. That may explain why the small rim that formed during pin tumbling is sufficient to prevent the round from chambering with a bullet seated into the case.
My purpose for posting this was to let others know that tumbling can put a lip on the case mouth that can cause a problem.
I appreciate your comments. Thanks