M&P Firing out of battery - what causes it?

coltman1985 said:

Are these reloads or factory rounds? Do you case gauge them all? Could have been a slight bulge in the case already that hindered it from chambering. More than likely though, it may have had a little to much powder in it!

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Man, that is not the result of a little too much powder. I would have to agree that that is the gun firing out of battery. In theory, it should not be able to do so (i.e. if a case fails to chamber, the gun should not set off the round).





To the OP, have you done a trigger job on the gun? If so, what did you do? Did you cut any coils form the firing pin safety spring?



Also check if anything is causing the firing pin safety to be jammed in the up position.





Whatever it is causing it, that gun is not safe at the moment.

Sorry for the delay in responding guys, I was at a football game yesterday. Anyway, here are the answers to the questions.



This was a reload though I have had factory rounds get stuck, too (Atlanta Arms, Winchester, and R&P). I Casepro all of my brass and use a Lee U-die on my 1050. I have case guaged all rounds and when I box them, I run a sharpie across the primers to make sure they are seated and to mark my brass. I am pretty sure it is not a primer problem. My load is 3.5 grns of Clays, 135 Grn Zero FMJ, OAL of 1.115. When fired, there are no classic pressure signs - primers are not flattened.



I have done a trigger per the online instructions that were posted here. I redeuced and polished the sear. Polished the contact surface of the striker. And rounded and polished the disconnector. I am beginning to think that I may be having a problem with the disconnector. Every now and then, when I rack the slide dry-firing, the slide will not go completely into battery. I notice this when I squeeze the trigger. The slide will actually move forward. So, I am going to take it down and see if I can tell what is going on. It does not seem like there is something restricting its movement.



Here is a pic of the headstamp...its Win brass from Winchester White Box 147s.

Dan,



Thanks for the feedback. I dry-fired the pistol and discovered that I could get it to fire with the slide just at 3/16ths of an inch out of battery. So, I took the gun down this weekend and checked what I could. First thing I discoverd was that the striker was sticking a bit when forward. I found that the striker channel was full of very fine brass shavings. I checked some brass and it appears that the striker has been dragging on the primers a bit (not retracting fast enough?). So, I cleaned that out thoroughly. I also checked the striker safety plunger. It seemed to moved freely.



Next, I started thinking that the trigger bar was engaging the sear too soon - perhaps I did not remove enough material from the engagement surface of the sear. Since I bought a replacement sear block (in case I screwed the trigger job up), I decided to remove a little more material from the sear engagement surface. That seems to have been most of the problem. The pistol will not longer fire with the slide that far out of battery. It will allow me to fire it with the slide "barely" unlocked (I can't even get a measurement), so I figure a little polishing might address that?



Now, my question is what is causing the firing pin (striker) safety to rise when the pistol is still out of battery? What are the possibilities? 1. trash causing it to stick? I think I have fixed that by cleaning it thoroughly. 2. Some foreign material in between the slide and the frame that is disengaging the safety? I could find no evidence of that. 3. The trigger bar engaging the safety pre-maturally? Could it be that I did not round the striker safety enough? The way I see it, if I reduce the engagement surface of the sear, the trigger has to travel more distance to engage the sear. In doing so, isn't it engaging the firing pin safety sooner, unless the contact surfaces on the firing pin block have been reduced?



I fired it yesterday, shooting some fast bill drills and it seemed to run fine. No indication on the brass that it was even close to being out of battery. No buldges on the brass. I am guessing that I am close to resolving the issue. I'll keep an eye on it. I have the USPSA Nationals next week so I have to go with it. Thanks again for the feedback.