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Light primer strikes


GregInAtl
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I have an M&P CORE MOS 9mm, 5" barrel. I've had the Apex Flat-Faced Forward Set Sear & Trigger Kit installed on it. The Apex kit comes with 2 trigger springs to choose from. I had the lighter of the 2 springs installed (by a qualified, experienced gunsmith) Ever since, I've had an issue with light primer strikes (about 4 or 5 out of every hundred rounds). I've had people tell me that installing a heavier striker spring would solve the problem, so I swapped out the striker spring and put a heavy duty one in. It did nothing to solve the problem. I would hate to put the heavier of the 2 Apex trigger springs in as I suspect that would do little to fix the problem. I was advised that Federal primers (I reload my own ammo) solve the problem and I found that to be true, but who wants to be limited to using Federal primers only, especially as scarce as reloading supplies are.

 

I've read that light primer strikes are a common problem with the M&P CORE.

 

Any thoughts?

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I run APEX triggers in multiple M&PS - original and 2.0. Only time I had light strikes was with a lot of Winchester primers. Are you having light primer strikes with multiple brans of primers, etc. or just one brand/lot? I have also seen primers that were not seated completely act like light primer strikes. Good luck

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I had the same issue with the same gun and same trigger kit - also installed by a qualified gunsmith.  I brought it back to him after several hundred rounds, and about 5% with light strikes...  he took it apart, and said he installed a stronger trigger return spring.  I'm still not 100% positive that was the issue, but it fixed it.  It's been perfect since with all types of ammo.

 

Consider trying that maybe?  Yes, I know it doesn't make sense.

 

 

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Hopefully ... your qualified/experienced gunsmith has adjusted the trigger bar so that it fully lifts the striker block out of the way before releasing the striker.

If the block is not fully "out of the way" it may bounce off the striker ... causing occasional light strikes.

 

Sometimes ... in an effort to reduce trigger travel ... people bend out the tail of the bar to start sear movement earlier. That is great but if that "bump" on the top of the bar does not travel rearward far enough it will not lift the block high enough to fully clear the striker.     

 

If you remove the striker block you can examine it ... If it is all beat up then you know the striker is hitting it. 

 

There should be other threads discussing this issue ... here is one ...

https://forums.brianenos.com/topic/246604-light-primer-strike-on-mp-40-after-installation-of-apex-trigger/

 

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  • 2 weeks later...

If it is a 1.0 M&P, everything you need to know is in the post above ^ and the link he referred to. I posted in that thread explaining the issue.

 

Easy test, and even easier because the gun is a CORE. Pull the optic plate, pull out the striker block, go shoot 100 rounds. If you get no light primer strikes, you know it's a timing issue. Reduce the gap in the trigger bar loop.

 

Feel free to shoot me a message if you have any questions. 

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I have not had that issue and have not used this product, but it claims it will resolve the issue.

 

Extended Striker Block Plunger for M&P®

After installing a custom aftermarket trigger in your factory S&W® M&P®, you may experience light primer strikes, which can lead to a failure to fire. To address this well-known issue, we offer an extended striker block plunger, which has been re-engineered to ensure positive ignition.

Even without a custom aftermarket trigger, the improved geometry of our Extended Striker Block Plunger makes a great addition to noticeably improve the feel of the factory trigger.

Fits all S&W® M&P® and M&P® 2.0™ (including Compacts) and S&W® Shield™, any caliber.

Fully machined from 17-4 Stainless. Drop-in installation.

 

https://www.edbrown.com/product/mp-esb-plunger/

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On 2/14/2021 at 7:21 PM, CenTX said:

I have not had that issue and have not used this product, but it claims it will resolve the issue.

 

Extended Striker Block Plunger for M&P®

After installing a custom aftermarket trigger in your factory S&W® M&P®, you may experience light primer strikes, which can lead to a failure to fire. To address this well-known issue, we offer an extended striker block plunger, which has been re-engineered to ensure positive ignition.

Even without a custom aftermarket trigger, the improved geometry of our Extended Striker Block Plunger makes a great addition to noticeably improve the feel of the factory trigger.

Fits all S&W® M&P® and M&P® 2.0™ (including Compacts) and S&W® Shield™, any caliber.

Fully machined from 17-4 Stainless. Drop-in installation.

 

https://www.edbrown.com/product/mp-esb-plunger/

 

Thanks for responding

 

I am curious whether this will fit the M&P CORE. In watching several videos for installing this, I noticed that for some of the older M&P's you have to take the rear site off but I don't think you have to take the sight off to install it on the CORE. Makes me wonder if it fits both CORE and non CORE models since the install is different

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1 hour ago, GregInAtl said:

 

Thanks for responding

 

I am curious whether this will fit the M&P CORE. In watching several videos for installing this, I noticed that for some of the older M&P's you have to take the rear site off but I don't think you have to take the sight off to install it on the CORE. Makes me wonder if it fits both CORE and non CORE models since the install is different

It fits all versions of the M&P 2.0 and the original M&P, to include the Pro, CORE and Compact.

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