Thread: Case lengthening when bump sizing

I think there are number of different questions and angles coming forth in this discussion, so I'm just going to clarify what I understand, as we may be talking about different things.

1. Repeated firings and sizings causes brass to 'stretch' or 'flow', requiring trimming of the cases. I think this is established fact and not in dispute.
2. Do cases 'stretch' or 'do the necks get longer' when the shoulder is pushed back during sizing? This I am unsure about. I haven't seen any fact to support this idea, and admittedly have not tried it myself as my measuring devices are not accurate to 3 decimal places, which is what I think the measurement could be if true. Brass is soft, and it seems likely that compressing brass during sizing of the shoulder and body would also bring the neck down with it. So I'm inclined to think that it is not true that necks can grow during sizing. So this is up for debate.
3. Cases chamber/headspace on the shoulder. A slightly long neck should don't prevent chamber if the shoulder has been sized correctly. I don't understand the argument that after sizing a shoulder correctly and within spec a case could not chamber. If it has been sized within spec of the chamber, it will fit inside. Perhaps this is or is not what the OP means, but it seems indisputable to me.
4. Sizing can happen 2 ways, full length, or neck only. The terminology of 'bump sizing' is somewhat misleading, as it is nothing more than full length sizing but only just enough to bring the shoulder within spec of the rifles chamber, but not all the way down to the shellholder. It seems some people do this with or without the expander ball fitted. Correct me if I'm wrong here but this is as I understand it.