non circular dents in spent primer


November 14, 2012, 03:26 PM
I have a ruger Sr9c. I recently noticed that the spent casings are exhibiting a non circular dent in the primer area. It looks like the regular dent plus a line travelling from the center of the strike to about two thirds across the primer face. I don't know if this is normal for auto pistols or if I have a developing problem. I have no other issues with the gun and it gets cleaned regularly. Please advise, thanks in advance.

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November 14, 2012, 03:42 PM
I have no answer, but I will say you aren't alone, I have several pistols that do this...leaving a drag mark with the dent. The dent also is in inconsistent areas of the primer, sometimes dead center, sometimes almost to the edge of the primer. All the pistols I have that do this seem to be striker fired as well.

November 14, 2012, 03:50 PM
You need to post a good macro type close up photo of the primer and the firing pin tip.

Wil Terry
November 14, 2012, 03:52 PM
THAT IS FIRING PIN DRAG, and it has only been around some autoloading pistols for some 90 years now. A heavier firing pin spring usually cures it.
And so it goes...

tightgroup tiger
November 14, 2012, 07:38 PM

I agree, I have an SR9 and it does the same thing. Nothing to worry about.

The firing pin is still extended while the slide starts back and as the case tips up to be ejected the firing pin drags across the primer face.

Nothing wrong with your gun. When I buy range brass, most all of the 9mms look like that.

November 14, 2012, 07:50 PM
AKA firing pin wipe.

November 14, 2012, 07:51 PM
Also known as firing pin wipe. Glocks are notorious for this.

November 14, 2012, 08:10 PM
Thanks guys. I feel much better about it now.

chris in va
November 14, 2012, 08:17 PM
Basically the case is being ejected while the pin is still making contact with the primer.

November 14, 2012, 10:46 PM
Also known as firing pin wipe. Glocks are notorious for this.

Not to mention the rectangular imprint Glocks make :)

As long as the gun is not having stove pipe ejection failures its nothing to worry about.

Some reloaders consider it to be a sign of overpressure, and it can be as long as you can be sure that the pistol doesn't do it on factory loads.

November 14, 2012, 10:57 PM
Have yet to see a glock that didn't do this, my taurus also does it, seen plenty of other brass out of various pistols that look about the same. Seems to be something that happens moreso in striker fired pistols from what I have seen.

Also primer flow from overpressure will usually look different.

November 14, 2012, 11:30 PM
Have a look at your breechfaces fellas. The odd imprint will show up there as well; as a small crater next to firing pin hole. Put there to give debris a place to go while allowing the pistol to continue to function. Conspiracy theorists will claim it's a micro-marking cut out to positively ID brass.

November 15, 2012, 05:58 AM
Conspiracy theorists will claim it's a micro-marking cut out to positively ID brass.
That's why after picking up all my brass I throw down a [gloved] handful of decoy Aluminum and Berdan primed cases to misdirect those who are after me.

November 15, 2012, 09:02 AM
I like your style and your thinking! Nothing says "huh..." like a staged scene;-).

November 15, 2012, 09:25 AM
Interesting, I never knew this.

November 15, 2012, 10:35 AM
My M&P9 wipes primers too. Doesn't appear to vary with ammunition, and doesn't affect function. I ignore it.

November 16, 2012, 07:25 AM
Also known as firing pin wipe. Glocks are notorious for this.

I've fired over 300,000 rounds of my reloads through my various Glocks. I've NEVER seen a case of firing pin drag on any of the fired cases. Glocks do exhibit a rectangular firing pin strike on fired brass, but that's irrelevant to this discussion.

November 16, 2012, 11:34 PM
Well hentown I guess we are in the presence of the final word.

I have seen different on my Glocks. Does not make your experience of inspecting 300 thousand cases invalid though.

November 17, 2012, 07:23 AM
In my experience, I noticed this in my striker-fired guns - SR9c, M&P, Taurus 24/7, and Kahr CW9. My CZ85 and Taurus PT92 did not do this.


November 17, 2012, 07:56 AM
In the Glock, the firing-pin wipe is contained entirely WITHIN the extruded area of the primer, so, it'll be there, but probably not very visible without a microscope. This characteristic is seen in all pistols that use the Browning-style (link or cam) method of locking the breech; as the rear of the barrel drops to unlock, the primer is still pressed tightly against the breech-face, and that's what leaves these marks.

November 17, 2012, 08:05 AM
I'm certainly no "final word," but I can attest that none of my Glocks ever exhibited any primer wipe. If one has to examine a case with a microscope, in order to see the so-called primer wipe, then that's not the same anomaly described by the OP. ;)

I do suppose that my limited experience with Glocks would tend to invalidate the statement that "Glocks are notorious for that," though. ;) FWIW, a Glock's firing pin spring works exactly reverse of how a 1911's firing pin spring works, and that information is germane to this discussion. :eek:

November 17, 2012, 02:58 PM
Here's an example of a typical Glock "primer wipe"; in this case, the firing-pin drag is the triangular area outlined in red, and this is caused by the nose of the firing-pin remaining stuck forward out of the breech-face while the pistol unlocks (the barrel drops, while the firing-pin stays where it is), and you should see this to a greater or lesser extent in ANY Glock, because that design has no method for retracting the firing-pin until after the slide has reached its most rearward travel.

Jim K
November 17, 2012, 10:23 PM
It hasn't been around since auto pistols were invented, but it has been around since Browning invented the dropping barrel system. There are several possible causes, none of any consequence as long as what is causing it doesn't interfere with functioning.


November 17, 2012, 10:35 PM
Smith and Wesson Model 59

November 17, 2012, 10:52 PM
My PT145 always does this. Looks like you dotted an i

November 18, 2012, 11:27 AM
My PM9 does this- and it is noted as normal on pg 16 of the manual:

November 18, 2012, 01:07 PM
From the late Mr. Camp's Hi-Power's and Handgun's site.

The telltale firing pin "wipe" is present on the primer fired in the SIG-Sauer. This is typical and to be expected. The SIG-Sauer pistols purposely have a bit slower firing pin retraction to help thwart debris from entering the firing pin channel.

Bolded by me.

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