What's wrong with this picture?

[Snapshot]

...besides the horrible photo quality that is.

I was at the range and decided to use up some of my old carry ammo so I could put some fresh, unchambered stuff in. My old carry ammo was corbon HPs. I mixed them randomly in with some Speer RHTs. The corbons were a little louder then the speers but not enough to make me concerned. So I picked up the brass for reloading and noticed this:

Now I think something is wrong here but I want to get a second opinion before I get worried. Does anybody else see anything wrong?

 

[Cross-X]

So how well did the .357 Sig rounds group?

 

[Finalygotabeltfed]

Firing pin strikes on primers don't look right.

 

[EddieCoyle]

You're wrong. That's a great photo. What make/model of pistol?

I agree, the polished firing pin marks are a little creepy.

 

[jamz]

Yeah the firing pin ,arks look weird. Not blown out really, just... weird. Like they are filled in with putty.

 

[Jose]

Maybe someone prototyping a way to get around Commiefornia's new microstamping law?

 

[Snapshot]

Yeah the firing pin ,arks look weird. Not blown out really, just... weird. Like they are filled in with putty.

The "putty" look is just because of the photo. Eddie actually described it perfectly. It looks polished. If you see it at the right angle, the entire area that SHOULD be a dimple is flat and very reflective like a mirror.

One thing that I didn't mention because I didn't want to corrupt anybodies diagnosis is this: Another reason I wanted to shoot these rounds is that the bullets were just a hair set back in the case. Not enough to make me worry but enough that I didn't want to chamber them too many more times. I've heard set back and over pressure with 357 Sig can be a bit of a problem. I wish I had my chrony on me at the time.

As for the grouping: Very well. I was shooting like #%&@ that day for some reason but my brother did very well with it. I didn't measure the distance to the target or the size of the grouping (it was just a very casual shoot) but I was impressed. I seem to recall it being a fist sized group at whatever the first line at Boston Gun range is. The gun is a Sig 239

 

[GTOShootr]

I believe that's "primer flow". The primer around the firing pin hit flows back into a crater and then the little crater/mound gets sort of sheared off as the case is ejected, leaving that circle. You see it on some of the really hot .38 super brass but I also picked up some Remington 9mm brass like that, I think that's because they use a soft primer.

Do a search on "primer flow". In one article I read a gunsmith said it would lead to erosion of the firin pin hole.

 

[GTOShootr]

I've heard set back and over pressure with 357 Sig can be a bit of a problem. I wish I had my chrony on me at the time.

That's it.

http://www.38super.net/Pages/Factory2.html

Scroll down to the "pressure" section.

 

[Supermoto]

I'd say primer flow also, especially if you are shooting round that might have set back issues. you are running to much pressure. It can also cause bits of the primer to lodge in the firing pin hole and either cause misfires or slam fires

 

[Joe R.]

Cor-Bon ammo isn't loaded wimpy to begin with. Funny thing is the shiny part but look at the primer around the edge of the pocket. It doesn't show the typical " ballooning " that a overpressure load would give. I wonder if the primers are somewhat wrong or this is a typical picture for 357 SIG hotter loads looks like. They cycled okay though, right?

Joe R.

 

[GTOShootr]

There's excessive pressure from the setback. It is going to be there regardless of what primer is there. A thicker primer like a Win small rifle might not crater, it might flatten out or not show anything, but the excessive pressure is still there.