I have a M&P 9FS and I'm having inconsistent primer strikes with some ammo. First off the gun currently has 555rds through it and has the DCAEK and AEK in it. I had a failure to fire around the 400rd mark(very light primer strike)so I pulled the striker out thinking it might be dirty but it wasn't. I got to looking at my empties and all the Federals had good primer strikes, the ZQ1, S&B, and Gold Dot had inconsistent strikes. Some were good and some were light, but enough to ignite the primer. I'm trying to figure out if it's a gun problem or an ammo problem.

 I shot the gun stock for the first 100rds, then installed the DCAEK and fired a couple hundred rounds without issue. Then I installed the AEK and had the light strike about 40rds after the install. I've  fired a couple hundred rounds since without issues. I though maybe I needed to adjust the trigger bar loop since I had minimal overtravel but after watching the APEX video a second time Randy said that you only need a few thousands of an inch. If anything I probably have a bit more than I need.

 I would think that if the trigger bar loop wasn't adjusted right then all the empties would have inconsistent strikes, not just certain brands. Could it be that the S&B, ZQ1, and Gold Dots just have hard primers, and if so what would cause some of the empties to have deep strikes and some to have really shallow? I thought the striker was dragging on the sear since there was a light colored mark on top of the sear and towards the back, but I was told that is normal.

I know the easy thing to would be to only use the Federal, but the gun really likes the S&B and ZQ1, and until I can replenish my stock of 147gr HST's the Gold Dots were going to be my carry ammo(don't know now after seeing the varying primer strikes).

Any ideas on the cause of this?

ETA. before I installed the AEK I had only shot Federal ammo through the gun so I don't know how the gun would've acted with the questionable ammo pre AEK.

Step one revert to all stock parts and see if the issue resolves. If it does avoid further tinkering ( no matter what you do a gun that is not reliable is not an improvement no matter how much better the trigger feels etc)

I suppose it could be possible to have an M&P with a SHB that is higher or lower than it should be, thus requiring extreme adjustment of the loop to get an ideal break/reset point, which would cause the timing to be off with the trigger bar nub that interacts with the striker block either causing it to be too far forward or too far rear, which may mean during firing, the tip of the nub is contacting rounded point of the striker block instead of the flat part which is at the lowest point.... thus not pushing it totally out of the way......which would cause your striker to drag on the striker block.  To get a good break/reset location, did you have to open the trigger bar or close the trigger bar to any extreme point?

Look for any unusual wear on your striker or striker block which would indicate the timing of the deactivation of the striker block is off.

Otherwise, its possible you have a weaker than normal striker spring or are shooting ammunition with reallllly hard primers.

All of my M&P's get higher power striker springs from speed shooter specialties.

If those are out of stock, I will then just get a factory Glock striker spring, seeing as those are rated at 5.5 lbs, where factory M&P springs are rated at 5.0 lbs.

I've never had a light primer strike with a factory one, but I know some people have.  For extra security and positive ignition, all of my M&P's get a higher power striker spring and they have all functioned perfectly and have very solid primer hits.

Do you have an S stamped trigger bar or an H stamped trigger bar?

If it were me, I'd probably try a new trigger bar and a higher power striker spring.

I had lots of issues with my M&Ps.  Issues (no fire at all) with the original stuff resulted in installation of an APEX kit that solved those problems, for several months.  Then I had all kinds of issues.  No striker contact with the primer.  Indentation in the primer, but no ignition (2nd or 3rd time it would go off, usually).  Off center indentation in the primer, no ignition.

I put the Glock striker spings in the guns.  It didn't help my issues.

No strikes = may have been something called sear flutter.  The striker was slipping off the sear.

The off center striker contacting the primer (after not being caught by the sear) before the barrel was completely in position/locked up.  Or still sear flutter.

The light strikes = may have been the striker block not being completely in the correct position to allow the striker to move freely, the striker went forward, but was slowed down by the striker block and pushed it out of the way.  Someone called this a "timing issue".  The sear released the striker before the striker block was completely up out of the way (the APEX striker block).

I replaced the APEX parts with factory parts and got rid of the sear flutter issue.  I still had light center strikes on the primer.  So I tweaked the hump/bump that pushes the striker block upwards (took a pair of pliers and slightly twisted it to the rear).  That seems to have taken care of the light strikes issue.  I've been through 2 shooting sessions so far without a single failure to fire.  I'll have to do some more before I pronounce the gun reliable again.  Then I still won't use it as I've found something better.  The M&Ps will just go in the safe.

Good luck with yours.

The trigger loop was set at .016/inch from the factory and I opened it up to .017 and there isn't any noticeable movement after the striker drops, but if I put a 3/32 punch in front of the factory trigger stop on the back of the trigger guard the gun will fire right as the trigger contacts the punch. This gives me about .022 of a gap at the top rear of the trigger where APEX says to check overtravel. Maybe this is too much?

I have the H stamped trigger bar.

I'll go ahead and order the heavier striker spring if it's in stock. Will there be any issues with pierced primers if I run a heavier spring and use ammo with soft primers? I also have a factory glock striker spring in my parts box so maybe I'll try that until I get the extra power spring from SSS.

here is a picture of the sear on my gun. Don't pay attention to the thin scratches, I did that with a punch when I checked to make sure the sear spring was working correctly. The striker leg has a polished look to it also.

I had issues with light primer strikes a while back as well.  The gun ran flawlessly for a good while, and then started giving me issues.  I had a new trigger bar installed, had the stock sear reinstalled (was running an APEX hardened sear at the time), made sure the striker block was moving out of the way, and made sure that the striker channel and striker assembly was cleaned.  Still had issues.

When I contacted S&W it looked like it was the striker assembly, which was still the first generation assembly, that was giving issues.  Swapped that out with the second generation striker assembly and haven't had an issue since.

I'd recommend taking a look at the striker spring first, then the trigger bar and loop to make sure it's in spec, then that the striker block is moving out of the way enough, and then seeing if the striker assembly needs replacing.  I'd highly recommend getting a ghost plate to watch the parts moving to see if anything is getting hung up.

http://www.amazon.com/GHOST-Ghost-Armorer-Piece-Glocks/dp/B003WG2QHO

went out today after putting the Stock Glock striker spring in and shot 50rds or ZQ1 and had three failure to fires. Two went off on second attempt and the third still wouldn't go off even after 5 tries and having the primer totally caved in(this must have been a bad primer). I put the stock trigger back in and fired a few rounds of ZQ1 but the primers all looked the same as before.

My question is, I noticed that the slide has a small recess below the firing pin hole, is this normal and what is it for. I noticed on the primers that have light strikes but did fire there is a pretty good mark that is the shape of the recess, but on the primers that have a deeper strike the mark form the recess is barely noticeable. I pulled out the test fire case (it is a Winchester casing)and it has a nice deep mark on it. Here are some photos of the brass Win. test fire casing and some nickel coated casings from some Gold Dot so you can get an idea of the primer strikes I'm getting.


here is a picture of the recess below the firing pin hole, it's a little blurry but you can make out the shape of it.


Also the spare striker I got from Speed shooters is the current Gen5 version, is that any different than the one that is in my 2013 test fired gun? They both look the same to me.

I'm just posting some encouragement for you, I've got the same problem with my Pro 9mm and I've been thinking of following the same process you are.  In fact I've already swapped strikers between my Pro and 9c, without any change in reliability.

My next change will likely be striker springs (Glock std spring likely as I can't find the extra-power M&P in stock) and maybe the trigger bow if the spring doesn't work.

Good luck!  Keep this thread updated please.

another update. I put the stock trigger back in and adjusted the loop back to factory spec and it made no difference. I also checked to make sure the striker wasn't dragging on the striker block and there were no marks on the SB that would indicate contact with the striker. I haven't tried a different trigger bar yet but might in the future.

I've also read on another forum that someone had light strikes and it ended up being caused by the extractor being too tight from dirt and keeping the slide out of battery just enough that the gun would still fire. I guess there was enough slop in the system that the casing wasn't seated all the way and would move forward when the striker hit it. I might pull the extractor out and clean it.

Right now I'm just not going to use ZQ1 ammo since it's the only stuff that the gun has actually failed to fire with. I'm also starting to wonder if some of those light strikes are really as light as they seem. Maybe the primer is getting smeared a bit during the unlocking of the barrel. Some of those strikes on the ammo that did fire are just as light or lighter than the problem rounds.

A new trigger bar likely won't make a difference.  It sounds like it's either the striker or the ammo, but since it's specific to one type of ammo it's likely the ammo.