Regarding the flat primers, I recall visiting the pressure test facility of a major ammo company many years ago. After watching a routine test (back in the days of copper crushers), my host handed me a few of the fired cases. He asked, "What do you think?" The primer was flattened all the way to the brass. With all my wisdom I intoned that, "The primers sure are flat; pressure must be way up there." He replied, "No, actually the pressure is lower than usual. The firing pin drives the case forward, the primer backs out shortly after ignition, then the pressure drives the case back against the bolt and the protruding primer gets smashed. Happens all the time with the .35 Remington and its small shoulder. We just call it a "nailhead"."
So ended my faith in reading primers.
Buford verified the same process in his video.
