M&P fires every other round - MP-Pistol Forum

M&P fires every other round

This is a discussion on M&P fires every other round within the MP Pistol Tech Help forums, part of the Smith & Wesson MP Forum category; First round chambers and fires, second round chambers, won't fire. I eject the round to inspect. It is not indented, so the pin never hit ...


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Old March 6th, 2016, 04:27 PM   #1
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M&P fires every other round

First round chambers and fires, second round chambers, won't fire. I eject the round to inspect. It is not indented, so the pin never hit it. After ejecting the round that doesn't fire, the next one chambers properly and fires and ejects. Next round chambers, doesn't fire, and so on..

Gun has many many rounds through it, but it is very clean.

Thoughts.
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Old March 6th, 2016, 07:29 PM   #2
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Welcome to the site!
Is the gun completely stock?
When my M&P 9 started doing that(although not that regularly) after I installed an Apex flat faced trigger and forward set sear kit, I ended up solving it through trigger bar loop adjustment and straightening. Another possibility is a damaged striker. I am sure there are people here more knowledgeable than me who will have other ideas.
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Old March 7th, 2016, 06:34 AM   #3
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When you hand cycle it, you pull the slide all the way back and then release it and then that round will fire. But on normal recoil, it doesn't. Sounds like the sear isn't catching the striker on recoil. One possibility is if you have the old sear cage with the small spring, you may be experiencing sear flutter. Also, are you using lower power reloads that may not be completely cycling the slide? Are you experiencing any failures to feed? More details would be helpful.
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Old March 7th, 2016, 02:31 PM   #4
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Interesting! Welcome to the forum! Do you know if the trigger has been worked on?
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Old March 7th, 2016, 06:34 PM   #5
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Do you get a 'click' of the trigger when the round fails to fire?

I'd pull the striker out and make sure it's clean. Don't lube it at all when re-assembling.

Another place to check is the striker block - does it move up a down freely or does it stick?
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Old March 11th, 2016, 07:07 PM   #6
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Good feedback everyone. The gun is very clean, and nothing is sticking. I've tried several brands of ammo, same results. The gun has not been modified in any way. There are no misfeeds, and when the trigger is pulled, there is no sound or action at all. It acts like it did not reset.
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Old March 11th, 2016, 08:49 PM   #7
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Sounds like you need to call S&W and talk to them, they will probably issue a pickup on it for service. Their service is quite good, turnaround is usually very quick.
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Old March 12th, 2016, 03:28 AM   #8
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The M&P is a fairly simple pistol so it seems to me that there are a few things that it could be: a broken/weak sear spring, worn sear,worn trigger bar or broken/worn striker "leg".
My guess is that it is possible that when firing, because of a worn part, the sear is not able to hook onto the striker "leg" when the slide cycles forward, but hand cycling is allowing it to do so, perhaps due to the different speed or force applied to the slide when hand cycling.

Another possibility is that the slide is not fully returning to battery, preventing the pistol from firing. This could be the result of a worn recoil spring.

These are a few of the possibilities just off the top of my head, but unless you want to dig into it and start replacing parts yourself, it is probably best to just ship it back to S&W and let them diagnose it
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Old March 12th, 2016, 06:28 PM   #9
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Does your gun have a magazine disconnect?
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Old March 13th, 2016, 03:11 PM   #10
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Quote:
Originally Posted by G56 View Post
Sounds like you need to call S&W and talk to them, they will probably issue a pickup on it for service. Their service is quite good, turnaround is usually very quick.
+1 !
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Old March 13th, 2016, 07:15 PM   #11
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not sure if it is cool or sucks but mine did the same thing today. It is a new to me M&P pro .40 with apex fss flat face trigger job with about 200 rnds thru it and test shell shows 7-30-14. The person I got it from installed the trigger and didn't tell me about any problem and I have known him a while and don't really suspect anything wrongful about this yet. I took it out for the first time and shot it just before a match when it happened 3 times in a row so gave up and used my fs. So tonight I am looking online and find a few things talking about what makes this reset and I look at both my pistols lowers which have the fss kit and the fs that works perfect is different. Looking down from the back there is a considerable difference on how much the sear goes down and how much it goes back up. The pro is almost half as much in height. I will have to pull both triggers out to see what the loop looks like under the sear and adjust. I am not going to send it to S&W if I don't have to and would uninstall the kit before I did. I also noticed that even before I shot it that it seemed stiff and the trigger pull seemed heavy with the comp. trigger spring in it but just shined it off as be not really broke in. Anyone have any ideas what would bend the trigger bar loop? anyways I will not really have time until later this week to mess with it and will try and get pics and get back with you.
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Old March 13th, 2016, 08:43 PM   #12
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Never send a pistol in with any custom parts in it, you run the risk of S&W pulling them out and toss them, it has happened! So put the stock parts back in it and test fire it again, it would be embarrassing to take the custom parts out and have it work properly when its sent in. Its always possible the custom parts were not installed properly.

S&W warns against sending any custom parts or custom sights back to them when sending them in for service.
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Old March 14th, 2016, 04:03 AM   #13
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Quote:
Originally Posted by G56 View Post
Never send a pistol in with any custom parts in it, you run the risk of S&W pulling them out and toss them, it has happened! So put the stock parts back in it and test fire it again, it would be embarrassing to take the custom parts out and have it work properly when its sent in. Its always possible the custom parts were not installed properly.

S&W warns against sending any custom parts or custom sights back to them when sending them in for service.
I agree with the trigger group custom parts, especially with this problem, but the sights seem a little excessive. Maybe they are going to pull the FPB and will not put aftermarket sights back on.

I guess if one sent a gun back stating it is shooting low, left, high, etc., I could see them pulling the sights as well.
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Old March 14th, 2016, 06:13 PM   #14
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I found a couple really good explanations of what looks like our problem, and/or how to fix it.
m&p trigger bar
https://www.youtube.com/watch?v=bdBpFlGtnFw
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Old April 29th, 2016, 07:35 AM   #15
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Do you have an update on what you ended up doing? Fixed?
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