I noticed this after reading some reloading books. The books said to pay attention what the primer looked like after firing. I have not run any reloads through this gun yet. I decided I need to see what normal looked like first. This is a Glock 27 I have run around 500 rounds through it. My question is this gun is leaving a different looking hit on the primer then my other guns. I have a G21, G30 and a Kimber 1911. Is this something I need to worry about?
The .40 cartridge tends to start the gun out of lockup quicker than other calibers. In the earlier years of the cartridge, that was blamed for the guns being less accurate than other calibers.
According to a knowledgeable friend, that's why Glock puts more clearance in the .40 chamber... to change the pressure curve & slow down the unlocking action. I believe that design change is more apt to aid a possible KB than the "unsupported" chamber idea. It certainly is the reason for the bulged .40 cases, since the bulge is around the entire case & not just at the 6 o'clock position.
I believe you are asking if the firing pin mark is normal? Yes, if you look at the firing pin on a Glock pistol you will see that it is shaped differently than most pistols which explains the mark they leave. You can typically pick up any brass at the range and tell which were fired in a Glock by the firing pin indentation.