It is very hard to interpret primers on auto mechanisms, or even manually indexing firearms. If the whole primer has backed out, it might be due to low case pressures and high friction between the case and chamber. Sometimes primers appear flat because of high case to chamber friction. The case gets fixed, the primer backs out, then as pressures rise, case sidewalls stretch so the case head stops at the breech face. This stuffs the primer back in the pocket, but the primer is mushroomed for being out of the pocket, and when it gets stuffed back in, it appears flat. This is why I do load development with lubricated cases, to keep the primer in the case, and to note when the primer actually flattens due to increased pressures.
An aggravating factor is large firing pin holes. Remington used to drill their M700 firing pin holes oversize so the primer would cup around the firing pin. Remington claimed it provided better gas sealing. This practice may be followed by other manufacturers. It sure cause the owner of that M700 concern. It is just another example of how hard it is to judge pressures by primer appearances, it is more than hit or miss.
Absolute positive indications of over pressure are blown primers, leaking primers and pierced primers. When these are encountered it can be certain the powder charge was overmax well before the primers blew. With a revolver, when you have to beat the extractor star open, that's a clue pressures are too high. Autopistols, and for that matter semi auto rifles, the mechanism unlocks itself, so you don't get the feel of sticky extraction. I look for signs of over acceleration of the mechanism. Such as malfunctions that occur when breech pressures are too high at unlock, such as bolt over rides, or the mechanism being slammed too hard, and ripped rims! I know hard recoil and too fast of slide operation are subjective, but, if you get used to your pistol, you will notice this, along with the distance a shell is ejected. The faster the slide moves, the further the shell gets tossed.
Some mechanisms open and eject faster than human perception. A bud has a H&K P7, a gas delayed action blowback pistol. That pistol also has a fluted chamber to break the friction between case and chamber.
I watched him shoot and the slide opened and closed faster than human perception. For a mechanism like that, I would simply find the lightest load that would function the thing, and then go a half a grain above that, till the pistol always cycled, depending on the weather. I was told by two owners of these things, that 9mm rounds that functioned their Beretta's did not have enough power to function their P7's. Sometimes you have to load for the pistol.
it seems to be the gun and breech face but when you have any issues it is good to post what exact powder charge, COL and firearm. Eliminates folks guessing on what may be the problem
