The pre and immediately post WW2 experimenters such as George C Nonte Jnr wrote extensively about the ability of firing pin strike alone to bump shoulders. In a much more cost conscious age when reducing components costs and using a single rifle for many purposes were desirable, you had very light, or even ultra-light, loads with light home-cast bullets and very small charges of pistol powders. Nonte used 2.5-5gn charges of Bullseye in various full-size cartridges like .303 British and .30-06. No press or dies were needed as cases didn't expand and bullets (or off the shelf buckshot balls) were simply hand-pressed into the case-mouth with a dollop of Vaseline, cases were decapped with a piece of dowelling with a small diameter nail in one end ............ and so on.
All such writers stressed that the cases used in such ultra-light loads, especially if rimless, had to be segregated from those used in full-power loads as they developed seriously excessive headspace over the course of repeated firings, the low pressures such charges generated failing to blow the shoulders forward again on firing and so each successive use saw the shoulder clearance increase. P O Ackley in (I think) Part 1 of his Handbook for Reloaders and shooters carried out an experiment which involved such light loads and reached the point where the firing pin reach was no longer adequate to ignite the primer after multiple firings and shoulder 'bumps', and had to engineer a firing pin tip extension to carry on.
So, this phenomenon exists, albeit the sort of rifle Nonte and others were using usually had heavy strikers and powerful springs which presumably imparted much greater energy to the pin tip than many of today's actions, especially custom match orientated designs. Whether the OP's possible over-annealing led to this situation on a single firing seems rather problematic with multiple other possible causes, but that's my opinion only FWIW.
