The S&W M&P problem thread

[Dos Cylindros]

I have seen many Glocks auto forward. At my last agency I would see our issued G22's and 23's when instructing on the range. If you slam the magazine in hard enough and at the right angle Glocks auto forward as well.

[T2C]

On October 3rd I was shooting with several other people when a friend had a problem with his M&P 40. The pistol would not fire and the primers had very light firing pin marks on them. We tried different brands of new factory ammunition and the problem persisted.

We removed the slide and the firing pin protrusion looked good. With the firing pin safety depressed the firing pin moved freely. The pistol was reassembled and it still would not fire. This was disappointing. He had to switch out and shoot another pistol for the day.

The pistol is fairly new and has had roughly 3,000 rounds fired through it. It is completely stock without any modifications. He is going to contact Smith and Wesson about warranty work. Once the issue is corrected, I will post an update on what it took to get the pistol operational again.

[T2C]

I have seen many Glocks auto forward. At my last agency I would see our issued G22's and 23's when instructing on the range. If you slam the magazine in hard enough and at the right angle Glocks auto forward as well.

I have seen the same thing at my agency.

[cmkirkham]

First, I'm no expert on this, but made a few observations recently.

I've never had a FTFeed with my 9FS or 9c during firing, but can induce one by slapping the magazine in with enthusiasm, particularly with JHP ammo, but it has happened with FMJ as well.

Seems to me that if you drive the magazine in hard, the slide begins to move forward before the round is up high enough to feed properly so it gets caught on the lower edge of the feed ramp, though I'm not quite sure about the mechanics of this. Perhaps the magazine spring is not quite stiff enough and and aggressive slap allows the round to bounce off of the feed lips and the nose of the round drops low enough to get caught on the bottom of the feed ramp.

I've also noticed that I can get the slide to drop by slapping the bottom of the magwell without trying to insert a magazine, and that if it doesn't occur on the first try I can watch the slide stop creep down the notch in the slide a little bit more with each slap. This makes me wonder if the propensity to autofoward isn't a function of there not being enough friction between the edge of the slide stop and the slide.

Has anyone ever tried to modify the rear edge of the slide stop so that it is more vertical in the engaged position, and perhaps the rear of the slide notch, too? Seems like this may make the engagement between the stop and notch more positive and might reduce the probability of autoforwarding. I do wonder if this would impact the function of the slide locking back on an empty magazine reliably, or make dropping the slide too difficult. I've read of M&Ps that required very high effort to drop with the slide stop, but mine are far from having that problem. I've included a photo of the slide stop with a yellow line indicating the angle that I wonder might help. While I'd be willing to mess with the slide stop, I'm way less inclined to mess with the slide, since the stop is cheap to replace.

Thoughts on any of this?

[RogerinTPA]

On October 3rd I was shooting with several other people when a friend had a problem with his M&P 40. The pistol would not fire and the primers had very light firing pin marks on them. We tried different brands of new factory ammunition and the problem persisted.

We removed the slide and the firing pin protrusion looked good. With the firing pin safety depressed the firing pin moved freely. The pistol was reassembled and it still would not fire. This was disappointing. He had to switch out and shoot another pistol for the day.

The pistol is fairly new and has had roughly 3,000 rounds fired through it. It is completely stock without any modifications. He is going to contact Smith and Wesson about warranty work. Once the issue is corrected, I will post an update on what it took to get the pistol operational again.

Has your friend removed and inspected the striker assembly and checked for excess build up of primer sealant in the channel and on the spring or damage to the assembly itself?

[T2C]

Has your friend removed and inspected the striker assembly and checked for excess build up of primer sealant in the channel and on the spring or damage to the assembly itself?

No he has not done this. He did tell me that since he last fired the pistol he cleaned it thoroughly and applied Frog Lube. I did not see any build up around the firing pin opening on the slide and the firing pin moved freely when the firing pin safety was depressed. There was pronounced firing pin protrusion when we checked the pistol at the range.

[Cincinnatus]

I think it sounds like a broken striker. Does firing pin protrude without inducing it to do so?

[T2C]

I think it sounds like a broken striker. Does firing pin protrude without inducing it to do so?

No it does not. When you pull the tail of the striker to the rear, the safety captures it and there is no protrusion.

[C4IGrant]

On October 3rd I was shooting with several other people when a friend had a problem with his M&P 40. The pistol would not fire and the primers had very light firing pin marks on them. We tried different brands of new factory ammunition and the problem persisted.

We removed the slide and the firing pin protrusion looked good. With the firing pin safety depressed the firing pin moved freely. The pistol was reassembled and it still would not fire. This was disappointing. He had to switch out and shoot another pistol for the day.

The pistol is fairly new and has had roughly 3,000 rounds fired through it. It is completely stock without any modifications. He is going to contact Smith and Wesson about warranty work. Once the issue is corrected, I will post an update on what it took to get the pistol operational again.

It is kind of hard to trouble shoot a pistol without you having it in front of you, but will try and give some helpful suggestions.

1. Remove the the Striker assembly. With a flashlight look into the channel. You should see the channel liner. Make sure there is no lube or debris in there. Make sure the spring has tension on it and the retaining cups are in place.

2. Push up and down on the striker block to verify that it freely moves. Make sure that you engage it at an angle (like how the trigger bar does). If possible, remove it and inspect the channel for anything unusual. It is also possible that the striker block engagement section of the trigger bar is too short and is not fully depressing the striker block. So compare its height to another M&P.

3. I assume that the striker is being released by the sear (meaning you can hear and feel it moving forward). If you cannot, then pull the SHB and inspect the sear plunger and spring. Does it have the big or small sear plunger? Might have a dead trigger issue going on (doubtful though, but needed to cover it).

4. Pull the barrel. Put a live round in the chamber. See how far below the case is from the hood (calipers are useful here). It is possible that the case is sitting too deep in the chamber for the striker to reach it. Again, highly unusual, still needs to be checked out.

We left out asking about the quality of the ammo as we assume that it is Federal, Winchester, etc and is not reloads or russian.

Look forward to hearing what the problem is.


C4

[T2C]

Ammunition used was Federal, Winchester and UMC. I'll contact the owner of the pistol and ask if he has heard anything from Smith & Wesson yet. If not, I may tear the slide down and inspect the parts.

On the same outing another shooter fired a M&P 40 with over 5,000 rounds through it. He fired roughly 400 hundred rounds without issue.