Are you measuring the distance from the trigger bar pivot point to the back edge of the pickup? that's where the difference is and you typically need a gauge to measure it correctly.

Aside from the trigger bar length, we've also seen striker block holes in bad locations that certainly don't help the issue. It's a matter of tolerance stacking.

If you have another M&P, you might try a different slide.

There have been isolated cases of the perfect storm where the slide, trigger bar and frame are all on the ragged edge of tolerance causing the trigger OT stop to need to be modified. If you remove .015" from the OT stop location on the trigger, that will give you the throw you need to move the body back further. But the sear may need the previously stated mod to make the sear pickup after the striker block is out of the way.

You're using a factory barrel? That will make a big difference too.

You said that this is not related to timing, but I think what you don't realize is that the issue you're seeing is an extreme case of timing trouble.

I think you and I are on the right track. If we want to say that the trigger's inability to be pulled far enough back due to a physical attribute, then yes, I agree whole-heartedly that it would be an extreme timing issue which seems like it can only be solved via removing material.

I measured the overall movement from the back of the trigger ramp to a flat spot on the rear sear housing block and a pair of Mitutoyo digital calipers. Using the ID set of jaws (smaller), I opened them to the max gap that was present, zeroed the calipers, then pulled the trigger. Averaging out the 3 measurements gave me a number for the stock pull, then the APEX pull. I did find that I couldn't pull the APEX trigger any farther back, and at max pull the striker block engagement was not sufficient.

I am also very interested on your point about the M&P slide being milled within a certain tolerance, as I think that is something that may be a viable issue. I measured the striker block hole from the breech face, as well as from the rear of the slide (under the rear plate so I was measuring from metal), but I have no drawings to reference to see if the hole was located properly.

Thanks!

*** EDIT ***

Everything else is stock on the pistol, including the barrel... sorry for missing that!

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Check your over travel. If the kit is adjusted properly there should be almost none. If the loop is too far open it will want to break too soon. If you can't physically close the loop any farther and still are having this issue, it's likely you have a pistol that has too much tolerance stacking to make this kit usable. I have actually filed off some of the tip of the loop on shields to be able to adjust out more of the over travel because they are really bad with over travel. I've never had to do it on a full size but it's possible. There is also a difference in mass or stiffness between the trigger bars as well from what I have gleaned from my research. I've had similar problems in the beginning of using these kits but nothing I've never been able to fix.

The FSS kit should have more pre travel or "take-up" (although still very short) and very very little over travel.

Your issue is definitely a timing issue. The striker is essentially bouncing off of the striker block because it's not quite fully engaged, but enough to let it pass most of the way. The FSS is more susceptible to this issue than the others.

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Where did you remove material from the candy cane? The top, the back? The bottom?

Attached an image. If you take off material from the area marked in yellow, you can close the loop further.

Attached Images

20190112_191936.jpg (163.2 KB, 63 views)

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So if you look inside the loop of the candy cane, let's say it's coming from the right and goes left, loops up and to the top and comes back down to the right. The bottom of the tip is where you can remove some material (if you're closing the loop further) with a small file. It allows you to maintain the profile of the loop without compromising the profile of the loop. We're only talking about small increments of material being removed (thousandths at a time), but allows for the loop to be closed farther to delay the sear tripping and possibly fix timing (like what you see with striker peening).

Thanks!

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I still say put the stock stuff back in.

Thanks. That makes more sense and is reversible to return the candy cane back to the original orientation.

Could someone do me a favor?

I'd like someone that is not having any issues with their APEX kit (specifically the same kit I have, which has the forward-set sear, ultimate striker block, aluminum trigger) take a picture of their striker assembly out of the gun. I would like to compare my striker to those who are having zero issues and see if there's something different on my pistol that could be a one-off.

If you could take a picture with the striker sitting laterally, firing pin to the right, and the sear engagement surface (the "tail" of the striker) pointing down, I'd appreciate it a ton.

Thanks!

OK FWIW I installed kit 100-024 in my M&P pistol. First trip to the range I had four FTF all light primer strikes on five full mags of ammo, eighty five rounds all total. Hence my interest in this thread. I will admit that two of those were probably me dragging the slide with my thumb. I caught myself resting my thumb on the safety. So while I was thrilled with the new trigger, I was disappointed with the FTF light primer strikes. My groups tightened up significantly and I was still hitting low left on most of my shots, many were also in the center which was a rarity before. They were normally all low left.Now the whole group shifted up and to the right closer to the point of aim.
I also got my gun a nice Christmas present of the Apex Semi Drop in barrel. I installed that this past weekend. I watched each step of the video and did not have to file until I got to the point of pushing the barrel up into the slide. I purposely do not have a clock or wear a timepiece at my work bench and focus on finishing the job at hand. I'm guessing it took me about an hour all told. At the end of the install I put the old barrel back in the pistol to see the difference. Not only could I roll the old barrel around when it was in full battery, it also has a good amount of play forwards and backwards. The new Apex barrel had much less twist play and absolutely no forward and backward play. I watched the install video repeatedly and kept filing until my barrel clicked into the slide with the same amount of click I heard in the video. I put some lube in the range bag so I could put some on the new barrel before firing.
Went to the range two days ago and through a whole box of Blazer Brass 115gr and a whole box of Winchester 124gr NATO ammo with no FTF issues at all. The gun ran solid the entire time. So this time 100 rounds of varied ammo with no issues at all. Groups appeared tighter than before as well. So now I believe it is time to work on the indian and not the arrow, the bow is solid.
So either the parts had to learn to play together or the fact that the new barrel no longer has any forward / backward play solved my FTF light primer strike issue.