Primer cratering on Semi-auto pistol cartridges?

[Masterblaster1]

I have noticed that all the ammo I have ever fired in my Ruger P95 DC 9mm the spent primers appear to be somewhat cratered. This includes normal factory loads and handloads. Is this normal for most semi autos spent brass? I am going to shoot a known test load in my dads Sig and see if the primers distort in his as well. The test load is Blazer brass 115 grain FMJ. Other wise the cases look normal and the edges of the primers are still rounded like normal. I will see if I can come up with a good digital picture..

[Luckyducker]

My Son bought a used Berreta model 92FS and my brother-in-law had an identical pistol and while shooting the same ammo the B-I-L's 9mm cratered the primer dents while my son's did not.  I believe it is caused by a slightly oversized firing pin channel and should be of no concern if no other abnormalities are seen.

[Masterblaster1]

Yes! I compared the firing pin channels on my Ruger to my dads Sig and the Ruger was noticeably larger visible with the naked eye.

[Savage]

An over sized firing pin channel can be the problem. A weak firing pin spring can cause the cratering as well.
Savage

[Steve P]

Sometimes it is hard to distinguish between actual primer cratering and soft metal flow around a firing pin orifice.  Usually you can check the outside edges of the primer.  If still rounded, you are usually still within safe pressures.  If outside edges of the primer cup have obviously flattened against the bolt or receiver face, you are flirting with excessive pressures.

Steve