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Dewberry

Light strikes?

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so I haven't changed anything on the gun recently

its a 9mm pro that has...
an apex FSS trigger in it
the striker and striker spring are factory (i didnt want to run a lightened striker spring)
the striker block and its spring are factory (i didnt have the tools on hand to drift the rear sight out and i was happy with the resulting trigger so it never got changed out)
it has a custom over travel stop that limits the trigger travel
when it was all installed over a year ago the hoop on the trigger bar and the over travel stop were tuned so it would all work

since then it has had around 5000+ rounds through it

I had a couple light strike in practice a week ago, so I assumed the striker channel was dirty. I cleaned it and the problem only got worse.

I changed the striker assembly and the recoil spring to the ones out of my carry gun (full size m&p 9, which has 2500ish rounds through it.) and the problem got better but is still happening

my thought is that the part of the trigger bar that deactivates the striker block has worn down a little and not fully deactivating the block so the striker is glancing off the block and losing enough energy that its causing a light strike

any thoughts?

Edited by Dewberry

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I was going to suggest that maybe the striker block might be causing a problem. If you shine a flashlight into the back of the gun while dryfiring, you can see if the striker block is being activated. Also, check the striker for peening where the little tab would be making contact with the block if it wasn't fully lifted.

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I was going to suggest that maybe the striker block might be causing a problem. If you shine a flashlight into the back of the gun while dryfiring, you can see if the striker block is being activated. Also, check the striker for peening where the little tab would be making contact with the block if it wasn't fully lifted.

yeah ive played with it a little and the block is partially up when the sear would drop the firing pin, im just not sure if its enough to clear or not.

from looking at the striker i can definitely tell the two have been making contact, but i dont know how long its been happening or if its the cause of the problem.

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Makes me wonder if the Apex USB is included in kits because of the new tolerances introduced with the FSS or because it's just a better profile striker block and lightens the pull.

I'm running a re-profiled/polished factory striker block but I have the Apex spring under it. Two light strikes in about 1000 rounds but I mean, what do you expect with a 28oz trigger? :D

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Yeah, honestly I've been so busy this week I haven't had a chance to mess with it at all. I'm probably going to order some new springs and give apex a call next week.

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I have re-profiled the factor block and use it with the factory spring (only because I don't have an Apex spring -- otherwise I'd use it). I would think, if anything, the more rounded profiles make it LESS likely to be properly activated. Plus the Apex striker blocks were around long before the FSS existed, IIRC.

In case anyone is wondering, a lot of the Glock-specific sight pushers will work with the M&P rear sights just fine as long as you remove the back plate and striker before trying to insert them into the pusher. I use my MGW Glock pusher on my M&P's rear sights.

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Yeah, I know the fss kit has its own striker block that different from the USB. AMD they mention that's so it deactivated earlier in the trigger travel than the USB. I just wonder if it deactivates earlier than the factory block.

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I was not aware that the striker block in the FSS kit is different than the USB. The Apex website lists the kits as including the USB without mention of any differences. It would make sense, though, since it would have to be much less rounded if you wanted it to activate earlier. Does any one have a side-by-side pic of the two?

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Yeah, I know the fss kit has its own striker block that different from the USB. AMD they mention that's so it deactivated earlier in the trigger travel than the USB. I just wonder if it deactivates earlier than the factory block.

The USB came before the FSS kit. The new sear geometry forced Apex to modify the USB for more clearance for the reason you describe (i.e there was a Gen 1 USB which was not FSS compatible, but that was several years back). I understand that the current generation USB is compatible with both standard and forward set sears. I am surprised that a regular factory striker block works at all with the FSS, so it would seem you have been very lucky up until now. I would change out the striker block/spring for the ones that came with your kit, then replace the striker with an undamaged unit, before doing any further investigation.

You also don't mention which primers you are using... some are definitely harder than others.

Edited by StealthyBlagga

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Yeah, I know the fss kit has its own striker block that different from the USB. AMD they mention that's so it deactivated earlier in the trigger travel than the USB. I just wonder if it deactivates earlier than the factory block.

The USB came before the FSS kit. The new sear geometry forced Apex to modify the USB for more clearance for the reason you describe (i.e there was a Gen 1 USB which was not FSS compatible, but that was several years back). I understand that the current generation USB is compatible with both standard and forward set sears. I am surprised that a regular factory striker block works at all with the FSS, so it would seem you have been very lucky up until now. I would change out the striker block/spring for the ones that came with your kit, then replace the striker with an undamaged unit, before doing any further investigation.

You also don't mention which primers you are using... some are definitely harder than others.

If the OEM striker block is darn near square, which is the least desirable as far as trigger pull is concerned but most desirable as far as reliability since it gives the greatest distance where the trigger bar properly interface with the block, how does the Apex block work in instances where the factory block would not? Is it taller or does it have a bigger cutout for the striker?

Edited by TacticalReload

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Yeah, I know the fss kit has its own striker block that different from the USB. AMD they mention that's so it deactivated earlier in the trigger travel than the USB. I just wonder if it deactivates earlier than the factory block.

The USB came before the FSS kit. The new sear geometry forced Apex to modify the USB for more clearance for the reason you describe (i.e there was a Gen 1 USB which was not FSS compatible, but that was several years back). I understand that the current generation USB is compatible with both standard and forward set sears. I am surprised that a regular factory striker block works at all with the FSS, so it would seem you have been very lucky up until now. I would change out the striker block/spring for the ones that came with your kit, then replace the striker with an undamaged unit, before doing any further investigation.

You also don't mention which primers you are using... some are definitely harder than others.

If the OEM striker block is darn near square, which is the least desirable as far as trigger pull is concerned but most desirable as far as reliability since it gives the greatest distance where the trigger bar properly interface with the block, how does the Apex block work in instances where the factory block would not? Is it taller or does it have a bigger cutout for the striker?

IIRC the cutout geometry is different. Here is a photo I found online:

8c9b5334-2e26-480e-bebb-43a881db6b0a_zps

Changing the striker block is easy - just secure the slide in a padded vice, loosen the set screw and tap the rear sight over about 1/4", just enough the change out the parts. Use a non-marring punch (brass, even a scrap piece of wood or plastic can work) The FSS kit comes with a plastic dovetail tool to make the reassembly process really easy.

Edited by StealthyBlagga

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Thanks for the info, I was assuming they were the same internally and therefore the stick would have been more reliable. I will definitely get that changed out asap and get a new striker assembly.

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Oh and I'm running Winchester primers. So I don't think that's the problem.

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While we are on the topic of light strikes, I just received my Apex spring kit. Would you guys run the Apex striker spring and see how it performs or just stay away from it all together? I have a Pro and decided to just stay with the factory sear, but change springs. I know I can try it and see, but what does the forum think is best?

Thanks

ben

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I've not had a problem with the Apex striker spring in about 1000 rounds total (through four different guns). However, others here have had issues. Personally, I would install it and see if the difference in pull is worth bothering at all first. If you think there is a noticeable difference, I'd run it until you find that it's causing light strikes. In my experience, stoning the sear in the correct manner will make a much more significant difference in trigger pull weight than the striker spring will.

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Remove the striker block and see if the problem goes away?

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my thought is that the part of the trigger bar that deactivates the striker block has worn down a little and not fully deactivating the block so the striker is glancing off the block and losing enough energy that its causing a light strike

any thoughts?

It's at least as likely that the trigger loop is not lifting the front of the sear enough for the back of the sear to drop completely out of the way of the striker causing the striker to drag across the top of the sear robbing energy. The trigger loop is prone to wear especially if it is only partially under the sear lobe (part of the loop sitting to the right of the lobe so the friction is focused on the left half increasing loop wear).

One gun with an FSS has only .003" of clearance between the sear and striker when the trigger is pressed fully to the rear and another has .01". Guess which one has light strikes?

The FSS puts everything into a very tight window and the bent trigger loop is pretty variable from gun to gun.

This is only theory as I'm still fiddling but I'm betting changing the height and angle of slope on the trigger loop to tweak when the sear is actuated and how much it is moved will fix the problem.

I measured striker block interference with the striker and took a few thousandths off the top of the striker "wing" so that the USB clears it easier but still functions as intended and that made no difference. Also polished the entire striker & USB to ensure no edges were causing a hang up. No change whatsoever.

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When you put in your new striker block, also make sure you have the latest generation of strikers. I've had my M&P for a while and I still had a really hold striker, which does NOT play well with the Apex striker block in a very particular way: It hits it just enough that it sneaks by but shortly after it wear out the surface where the impact happens and the then the striker block no longer blocks anything as the you can push the striker with your finger past the block. Basically if you use an old design striker withe current Apex block, you will soon no longer have a working drop safety.

After I noticed this, I've tried again with an older striker block I had. Worked fine to start, a few hundred rounds later is worn off to the point of no drop safety. Put a new design one in, worked fine thousands of rounds.

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