no place to go
There is brass flow and stretch, or is it brass stretch and or flow? What I do know is I have never found skid mars on a case that has been fired multiple times.
I have tested cases for work hardening, not something that a reloader would do but in my efforts I have turned cases into accordions, or cases that resemble bellows. And I have cases that collapsed at the shoulder/case body juncture, the cases that have collapsed (as in the picture furnished by Jason75979) were caused by bad habits, or by following instructions on the Internet as in "all you gotta do to form a case is lube the case then take the full length sizer die to form a new creation.
Again, I am the forming die fan, the forming die shoulder is not as abrupt/radical as the full length sizer die shoulder, the forming die is case friendly, in the 'big inning' case forming and case sizing was case friendly, all had long tapered bodies and long tapered shoulders, there were no shoulders with steep angles. Then came Ackely and methods and techniques changed, not re loaders, just the methods and techniques, re loaders continued to attempt shoving brass around a steep shoulder, if the brass will not flow around the case body/shoulder juncture and the shoulder/neck juncture when sized the case squats and or compresses and folds, anyhow, I use the companion tool to the press, the feeler gage as a transfer/standard, because? I know the length of the chamber before I attempt sizing, and when forming long magnums to short magnums I use forming dies that will allow brass flow nicely around corners, THEN! there are donuts, the results of more bad habits.
Then there are the cute little dies that lock onto the neck leaving the brass between the head of the case and shoulder neck juncture no place to go when the ram is raised.