Thread: Help - What is going on with these primers??

Look at this image below which you posted, and compare to the primers on the picture you posted above: the rims of the primers are rounded still on the above picture, on the picture below here the primer is squashed completely flat at the back against the bolt face.

In the picture below, second one down shows the crater edge that @Max Headroom alludes to. In the pictures above about half of them show very mild cratering, the other half not, so some overpressure signs.

In the picture below, the fifth one down shows a crack at the bottom of the primer indentation where the primer wall has been thrust against and stretched over the firing pin, against the inertia of the firing pin. Primers 1, 3 and 4 show this effect more severely.