Light-strikes on a .40 M&P

[peter2772000]

Hello y'all.

New member from Canadia, but I'm an old whore in the world of firearms. I've got a particular issue with my M&P. I'm getting a light strike every 50 or so rounds. The primers on my reloads are Winchester small pistol standard, nuthin' special there.

I might add that until I started reloading, I'd never had any problems with light-strikes. The only issues I had were with the mag $hitting out of the pistol every 25 rounds or so. Three mag-release springs later, problem solved.

As well, are there any tips for lightening the trigger on these pistols. I know that cutting a coil or two off've the firing pin spring would prolly do it, but that would prolly magnify my light-strike issues as well.....

Thanks in advance for any tips/suggestions my south-of-the-border brethren may have for me!

 

[tomcatt51]

You're probably not fully seating the primers on your reloads if you weren't having the problem with factory loads.

 

[peter2772000]

Nope, the primers are fully seated (though I doubt that would cause these issues).

You can tell by the strikes on fired brass that the primers aren't being whacked with much force. Definitely a case of insufficient whoomp at the firing pin.

Thanks fer the effort, though....

 

[bountyhunter]

You can tell by the strikes on fired brass that the primers aren't being whacked with much force.

You'd be surprised. I set up comp guns a lot with "just enough" whack and when a round fails to fire, it looks like a very weak dent. But, the same round hit again with the same force will show a deep dent. The primer back flows against the head of the firing pin when it fires which makes the dent a lot deeper. You may have insufficient strike force, but looking at dents in unfired rounds is a bit deceptive.

Nope, the primers are fully seated (though I doubt that would cause these issues).

I'd wager that "light strike misfires" are caused by unseated primers more than any other cause by a WIDE margin. Don't know if yours are, but I couldn't count how many times that turned out to be the problem.

Does your gun have the stock mainspring? If not, you may want to try that.

Does this gun have a firing pin blocking safety? Sometimes, those will drag on the firing pin and cause light strikes.

 

[OKFC05]

Nope, the primers are fully seated (though I doubt that would cause these issues).

THE most common cause of failure to ignite with reloads is high primers.
The only have to be .001 high to fail and you can't detect that.
First hit seats them, second hit fires them.

If it only happens with reloads, that cinches it.

 

[peter2772000]

I guess it makes sense. Though I find it strange that this has never been an issue with my P-99 or any other semi I own in .40.
Additionally, I checked to see if the firing pin chamber is clean and that the pin moves easily in it, it is & it does. If no one here has ever had any such issue, then I guess high primers really are the culprit.

And yes, the gun is 100% stock with a firing pin safety.

 

[handgunner356]

I did have to replace the striker in one early M&P 40. To look at the engagemnet pad on the original striker it was completely flat up to the pin. The replacement and all the others I've looked at have a raised pad that would hold the striker about .050" further to the rear. I also thought that it was high primers but there hasen't been any issues with the gun since even with reloads. S&W did send me the pin without sending the gun back, but I am a FFL holder.

 

[magnum12pm]

If you want to lighten the the trigger on the MP, Do not monkey with any springs, not the route to take. I have never had a light primer hit on mine with more than 10 thousand rounds through it. The guys here are giving good advice, check out their suggestions. EM sent

 

[WR Moore]

I note you haven't had the problems till you started using your reloads. When did you last clean the firing pin tunnel?

Reloads frequently burn somewhat dirtier than factory loads-this is especially true with lead bullet reloads.

 

[peter2772000]

Magnum12pm, thanx for the email. Will definitely be trying it out. You da man!!!

WR; Yes, the gun's been cleaned inside-out. Definitely not the issue. And none of my reloads gave me this problem in my Walther P-99. I'm telling you guys, the primers definitely seem to be lightly wacked, yet the P-99 & Para 16/40 LDA smack & crater 'em solidly.

As well, I have checked that the striker assembly moves freely in the channel, it does.

Handgunner 356
"I did have to replace the striker in one early M&P 40. To look at the engagemnet pad on the original striker it was completely flat up to the pin. The replacement and all the others I've looked at have a raised pad that would hold the striker about .050" further to the rear. I also thought that it was high primers but there hasen't been any issues with the gun since even with reloads. S&W did send me the pin without sending the gun back, but I am a FFL holder."

Sure woulda like to have seen a pic of either your old striker or the new one so as to compare with mine. Anyone have pics of theirs?

 

[Fastbolt]

The first clickable thumbnail below shows pictures of both the original and revised striker designs, with the original design on the left. You can see how the bottom of the original striker's foot is flat on the surface facing forward.

The one on the right has the added material on the striker's foot to result in more spring compression and more resulting pressure for primer hits. This was a revision intended to resolve some early reports of 'light strikes'.

The second clickable thumbnail shows the same picture of the original striker with an actual new striker laid on the page above it.




You ought to be able to click on the thumbnail again after the hosting service displays each image for an even closer view.

Sorry for having to use a picture of the original striker but I don't have any of the original strikers available.

 

[HAWKEYE10]

check to make sure you are not taper crimping to much. thi could cause the bullet to go to far in thus a light hit. just a thought.
don

 

[RogerH]

Hey, Kenny at www.speedshooterspecialties.com has the extra power striker springs that will fix this problem without making the trigger pull any heavier.