M&P Breechface Oddness

T

TunnelRat

New member
Hi all,
I was cleaning my M&P Compact today when I noticed something odd about the breechface. It's hard to describe so I took the following pictures:







This pistol only has 720 rds through it from reputable manufacturers and was manufactured summer of this year. It's stored in a safe in a very dry basement. This picture is after a cleaning including a good scrub with a brass brush. If it's a machining issue it seems rather strange to me, but if it's erosion it doesn't seem very deep. Any thoughts?

-TR
 
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happened to have my 40c on me, mine doesn't look like that. could be a mistake in manufacture but I'm not familiar with how M&P slides are made: cast? forged? - I'm leaving that to the metallurgists here. What is interesting to me is that it looks like the black finish to the slide was applied with those pits already present. - I don't see bare stainless. At least we know it doesn't affect function. Other thoughts in my head but a long shot.. corrosive ammo? pierced primer/flame cutting? Was this one new or used? Seems like only the breech face is affected with the worse being lower part. Another long shot: perhaps the gun was previously wet and water stayed between the casing of a chambered round and the breech face.

Anyone else?
 
TunnelRat, I don't have an M&P, so can only say that I have never seen that tear drop shape to the firing pin oriface in any of the many and varied semi-auto pistols I've owned over the last several decades. A family member has an M&P Compact. I'll try to remember to ask him to have a look at his. As to the coarse machining, broaching I suspect, of the breech face itself, I can only say that if that is proper and correct for that pistol, I am disappointed in S&W. A smooth breech face is an asset, sometimes a necessity for reliability, in ensuring smooth movement of the rim and base of the case up the breech face during feeding. Some custom gunsmiths offer smoothing/polishing of the breech face as part of reliability work. That breechface is not due to your use or storage. Rightly or wrongly, that was done by the factory.
 
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Other thoughts in my head but a long shot.. corrosive ammo? pierced primer/flame cutting? Was this one new or used? Seems like only the breech face is affected with the worse being lower part. Another long shot: perhaps the gun was previously wet and water stayed between the casing of a chambered round and the breech face.
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All ammo was non-corrosive. This was a brand new gun. Gun was never to my knowledge stored wet. I'm an OCD fanatic.

For those that asked I am used to the firing pin hole being extended, I mean the marks around it and towards the bottom of the breechface.

A machinist I know that works at SIG making barrels had this to say:

Looks like heat has caused the metal to deform and collect impurities
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He thinks it wasn't properly heat treated at the factory and that's why the result is above.

I might call S&W and see what they have to say. Any other thoughts are welcome.
 
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It doesn't look like any kind of build-up to me, and that's not how he's describing it. It looks like a troubling amount of porosity in the metal. I'd make S&W take a look at it, regardless of whether it's impairing function at this point.
 
The first picture looks like there is something in the firing pin channel at the top, maybe dirt or some kind of residue. Not sure if that has any bearing on the question, but it looks odd.

Jim
 
Did you try scraping the pitted area to see if it scrapes off?
It kinda looks like carbon build up
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I scrubbed the heck out of it with a brass brush.

The first picture looks like there is something in the firing pin channel at the top, maybe dirt or some kind of residue. Not sure if that has any bearing on the question, but it looks odd.
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It was just a brass fleck.
 
My full size has the tear shaped firing pin hole... but not the pitting on the breech face.

Guess I know why the shield costs less than the compact model.
 
Tools that get used show wear anyways
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Yes, but starting off with wear isn't a good thing, nor is this typically an area that should show a lot of wear. I have pistols with 5k rds through them and the breechface looks the same as the day they were bought.
 
Ive had a couple of Glocks that have sort of similar markings. Semi rough breech faces that appear somewhat "unfinished". I think its probably more just tool marks than anything else.

The one I have now thats got a lot of rounds through it, had a pretty rough face, but a lot of its been polished out from use. I also see that circular "ring" more so on the guns that have a lot of rounds through them, and thats the portion of the face thats the most polished, which sort of makes sense.


One thing I have seen on Glocks that were dry fired a lot, were a couple of pics of failures in the breech face where that ring is. Like this...

breech2.jpg


While this one also shows a failure, what you see across the breech face as far as tool marks, those vertical lines, is what the couple of mine looked like when new.

breechface_damage_12.jpg


I havent had anything like those failures though, and I have a couple of them, that have bazillions of shots/dry fires on them, and no problems so far. I do use snap caps when I dry fire though.
 
The circle from the base of the case I get. The vertical lines being tool marks I also get, but these aren't vertical lines. The only way I could see it being toolmarks would be if the broach was worn and was tearing the metal as opposed to cutting it. I also use snap caps too for cheap insurance.
 
Do a google search on "rough breech face S&W M&P pistols" and look under "images". A couple came up, and one looks similar to yours. Even using that search, more of what comes up are Glocks. Seems to be more of an issue there.

If ts really bothering you, drop them an email. Im sure they'll probably get back to you.
 
AK103K said:
Do a google search on "rough breech face S&W M&P pistols" and look under "images". A couple came up, and one looks similar to yours. Even using that search, more of what comes up are Glocks. Seems to be more of an issue there.

If ts really bothering you, drop them an email. Im sure they'll probably get back to you.
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As I said in post 6 I plan to, but will have to wait until after the holiday.
 
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