Odd striiker marks on primer

EugeneNine · Aug 25, 2013

Anyone seen a pair of marks left on either side of the primer like these:

Left two are my reloads (Blazer case) , right two are factory loads (Win).

Do they look normal, I don't recall seeing the extra marks before.

SteveFi · Aug 25, 2013

looks normal to me - are you referring to the primer itself or small mark on the case? the primer looks normal for an m&P & if you have a small ding on the case next to to the primer that is from the ejector

scooter123 · Aug 25, 2013

Your pics are a bit too small and the lighting is not optimum, so it's sort of difficult to identify exactly what you have. So I'll just relay what I've observed on occasion.

Teardrop shaped impressions are rather typical with some semi autos and it's a result of the ejection process starting while the firing pin is still projected in front of the breech face. It's most common with semi's that use a direct contact type of firing pin, meaning the firing pin is projected in front of the breech face when the hammer or striker are in the full forward position. In semi's that use an intertial firing pin such as the 1911, these teardrop marks are usually an indication of a weak firing pin return spring that needs to be replaced.

Symetrical impressions on each side of the firing pin are typically a breech face impression. Some semi's feature either a small depression or projection in the breech face that leaves an impression on the primer. Usually these are the result of a hardened bushing being pressed into the breech face that isn't perfectly flush. It's not a problem as long as it doesn't cause feed or ejection issues but these are the type of breech face impressions that make a firearms examiner do a "happy dance".

Rastoff · Aug 25, 2013

Which gun are you shooting?

If it's a 9mm or .40S&W M&P, look at your breech face. Those two guns have a slightly tear drop shaped firing pin hole. That will give you what I think I see in your primers.

MichiganScott · Aug 26, 2013

If you look at the breech of the M&P line, you will see a tear drop divot that allows the primer to flow while the firing pin is forward and the breech beginning to unlock. It seems to be a design feature of the M&P line to assure function with all ammunition. The hotter the load, the more flowing you get, right to the point that the tear drop of brass will actually smear during unlocking of the breech.

flat_topp · Aug 26, 2013

SteveFi said:
looks normal to me - are you referring to the primer itself or small mark on the case? the primer looks normal for an m&P & if you have a small ding on the case next to to the primer that is from the ejector

I too get teardrop shaped striker marks on the primer with my M&P40. As mentioned by SteveFi, marks on the head next to the primer are likely from the ejector. I asked a similar question on this forum and got good, informative replies:

http://smith-wessonforum.com/smith-wesson-m-p-pistols/315590-nicks-burrs-head-spent-casing.html

EugeneNine · Aug 26, 2013

Thanks, I didn't think a teardrop shape since it is on two sides of the center circle. I just didn't remember seeing it a few months ago but have already deprimed all my original factory loads.

Dayvid23 · Aug 26, 2013

EugeneNine, funny story: I was shooting my 40 Shield yesterday, blasting away at a little pond. I have recently decided to start reloading, so unlike in the past, I policed my brass. I immediately noticed the exact same marks. I pictured doing the exact same thing you have done- lined up a bunch of shells, sending the picture on line to this forum, getting various comments, stuff like " send it to me, I will give you $5" or "get a glock" to "it fires when you pull the trigger, what ya worried about, momma' boy!" I smiled and just put them in the bag. So my comment is, yes it's normal, mine does it, and shoots fine. p.s. shooting into water is the bomb! No, it won't make you a laser eye, drop dead shot, but once in awhile it is fun to get some great feedback for each shot. Plus you can see how the bullets drop from longer distances!

EugeneNine · Aug 26, 2013

I had only noticed the extra marks after I started reloading so I was worried a little.

Odd striiker marks on primer

EugeneNine

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SteveFi

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scooter123

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Rastoff

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MichiganScott

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flat_topp

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EugeneNine

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Dayvid23

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EugeneNine

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