M&P 9mm, cratered breech face around firing pin hole

[aric84]

Not sure if this shout be here or in gunsmithing, but here goes....

I was out shooting with my coworker(browningsteve) and while he was shooting his M&P I was picking up some of his brass for him and noticed a strange bulge on the primers. Took a look at the breech face and there was what looked like gas cutting or something around the firing pin hole, you can tell the shape from the picture.... runs straight up and down. He said that he never noticed it before and that he has not noticed any sort of pierced primers before, but he is going to check his brass later today. Looking at some of the other cases he had, they all have the same marking and also noticed that they are varying in pressure quite a bit if you go by the primer flattening. I think he was using wolf remanufactured ammo, so the different cases might be causeing pressure spikes, but that is just speculation...
Oh, his brass is the ones with the silver coloured primers.

So, any clues as to what could cause this?

 

[TDC]

If the firing pin hole is anything like that on Glocks, its the shape of the hole that is causing it.

TDC

 

[IM_Lugger]

perfectly normal

I mean send the gun to me - it's not safe!

 

[enefgee]

Yes, there's a dimple under the firing pin it causes some odd primer marks.

 

[saskgunowner101]

Yup, the teardrop smudge is normal.....watch it change as you increase pressure with reloads.

 

[maka]

I notice the brass coloured primers do not have the mark. I would think that the silver coloured ons are Federal. They aew made of very thin metal.

 

[mudgunner49]

I notice the brass coloured primers do not have the mark. I would think that the silver coloured ons are Federal. They aew made of very thin metal.

Not appreciably thinner but certainly softer. Try CCI primers as the cup is a harder composition.

 

[aric84]

The cases with the brass coloured primers were fired out of my CZ Shadow, I just ended up with some of my coworkers brass since it was landing on my feet. A couple of the primers have a bit of flowing but I think those are also from his M&P, when I was trying it out with my ammo.
That's why I was wondering why there is so much flowiing in the primers, my CZ has none and his M&P has all sorts. Odd that they would make the breech face like that... But, if it is meant to be like that, then he will be happy that he doesn't have to bring it to the smith.

 

[ampegor]

My M&P 40 does the same thing to the primers -perfectly normal