S&W .40 M&Pc light primer strikes


the naked prophet
September 27, 2007, 11:56 AM
So the wife and I went and shot the .40 M&Pc again. Or, rather, she fired it and I shot three rounds.

Anyway, we've now put over 500 rounds through it with no lube and no cleaning. Only a few malfunctions in the beginning, all of the premature slide lock type (slide lock engaged with ammo still in the mag), with some stuttering thrown in as well (I'm betting the slide lock was almost engaging, and that caused it to hesitate before going into battery).

But after 500 rounds, it started showing a new problem. She would pull the trigger, and *CLICK* but no bang. Eject the round in the chamber, and it has a light primer strike. But the strike is way off to the side, at the very edge of the primer. This happened exactly twice, out of 100 rounds (did not happen in the previous 400+).

To me that suggests that the gun is so dirty, it's not quite going into battery, and that the barrel is not quite locked up - hence the cartridge not being centered on the breech face. Whatever mechanism it is that keeps it from firing when out of battery still allows the striker to protrude a minute amount (less than 1mm) from the striker channel. Is that an accurate assessment?

Has anyone else had this problem, or is my wife just crazy to want to see how long it would take to make the gun so dirty that it stopped working?

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September 27, 2007, 01:21 PM
I've had a couple of light strikes, but only early on and with ammo that has notoriously hard primers, so it wasn't clear if it was the gun or the ammo, or both.

What ammo are you using?


the naked prophet
September 27, 2007, 02:53 PM
Winchester white box FMJ with the flat point. Don't recall the weight, probably 165 grain.

The primer strike was very, very light. Just a pinpoint, really. With that weird conical tipped firing pin the M&P has. And it was on the very edge of the primer, not the center as all the fired cases were. All the fired cases also had quite the indent - it wasn't an ammo issue.

September 27, 2007, 07:59 PM
If it persists, let S&W know. They'll fix it. Fullsize M&Ps had a few problems with light primer hits right when they first came out, but I don't think Compacts ever had that problem, systemically.


September 27, 2007, 08:03 PM
Coronach... didja catch the part where he's torture testing it (hasn't been cleaning)?

I'd say probably not going fully into battery, barrel still tilted and pin not hitting correctly. Probably time to clean it up.

the naked prophet,
I wouldn't say she's crazy, I've tested for failure myself. Looks like you found the point though. Funny how different guns can be, My XD did somewhere around 1,000 rounds of DIRTY crud ammo before it misbehaved at all but my Kel-Tec P-3AT is so damned tight I'm lucky if I can go 200 rounds before it gets fussy.

September 27, 2007, 11:36 PM
Yeah, my PD put many thousands of rounds through an M&P in one session, and the gun didn't hiccup, so it shouldn't be that. Though, it could be, I suppose.

The tested gun was also a fullsize. So, I dunno.

Try cleaning it. See what happens. I've never placed much stock in extreme torture tests anyway. Would it be nice if the gun ran for a bazillion rounds without fault or cleaning? Sure. But since I really can't imagine a scenario not involving zombie hoards and a warehouse full of ammo in which I would ever be firing more than a 400 rounds or so without cleaning, I fail to see the point.


the naked prophet
September 28, 2007, 12:01 PM
Coronach, full sized guns are often more reliable than the compact version - as you well know. It's entirely possible that the full size will go thousands of rounds without cleaning, while the compact might choke at 500.

And the point of the torture testing (that my wife is doing, I'm not doing it, though I would if it was my gun) is not just to see how long it can be shot before it gets too dirty to work - it's also a measure of how much crud, accumulated by whatever fashion, it takes to make it stop working. If it takes 3000 rounds before it stops working, it'll probably tolerate say lint, sand or mud a little better than if it stops at 500 rounds.

We're cleaning it today and putting another 100-200 through it before we have a competition on saturday.

Not going to bother cleaning my glock 19 :D

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