After having read tons of threads here about how to cope with my decidedly gritty-feeling trigger on my pretty-much-brand-new, 50 whole rounds through it M&P 9mmFS, having watched the referenced Youtube a half-dozen times, and after having chased down a proper piece of brass rod to use as a drift, tonight I tackled the "polish the striker safety bore to eliminate burrs" process.

I'd done the test using rearward pressure on the striker blocker, and it seemed to fail this - - I could feel less-than-smooth motion as the part retracted.

Things went fairly easily, excepting my carefully-made sight-locating pencil marks wiping right off the first time I touched the slide . The set screw came out easily, the brass rod smoothly moved the rear sight aside, and I did not lose the spring or cover for the striker block.

Rather than using the harsh-looking dremel stone the gent in the video used, I opted for some fine rubber abrasive tools I use for smoothing engine parts, and finished with 1000-grit silicon carbide paper wrapped on a brass rod, hand-operated.

Things looked shiny-smooth in there when I was done. no perceptable burrs or drill marks left.

I cleaned everything carefully, put everything back together, and with the sear disconnect still lowered I tried the trigger pull.

Still gritty; no real change. Felt like you could count about ten little catches or snags spaced throughout the trigger pull.

This made me mad, so I started going over the FCG interior parts with a jeweler's loupe.

Quite quickly, I found a suspect; the raised 'cam' or actuator on the trigger bar that actually lifts the striker blocker, which is a stamped and formed piece of sheet steel, was not smooth on the cut diagonal face that actually moves across the bottom of the striker blocker; it looked as if the cutting die that made it had gotten dull, and there were about a dozen sawlike striations or grooves running across it. They were barely visible to my naked eye, but in the loupe they looked like a straight-cut file.

Aha.

I took some 1000-grit paper, wrapped it tightly around an old guage-block I have to stretch it flat, and carefully lapped out the grooves until the flat edge was mirror smooth, being sure to keep the angle unchanged & the edges unrounded. Took maybe 10 minutes work.

Put the gun back together, and tried the trigger.

Smooth
As
Butter

With a nice tactile break at the end.

I'm calling it a win, even if I did go the long way around to get there and had to spend 30 more minutes with a laser boresight getting the rear sight tapped back into hopefully the right place.

So, for the record, check the striker blocker actuator's rear diagonal face for tool-marks before you go after the blocker bore - - you just might save an hour or two.

Good stuff, UncaGrunny.

I noticed that rough trigger bar shortly after I got my 40C. I smoothed mine out using a lowly mechanical pencil eraser. I hadn't done any research about the gritty trigger & now that I know what the problem is I'm finding all kinds of posts concerning grittiness like yours above. At first I figured that I didn't want to experiment with any thing too abrasive & likely to take too much material off of the bar. Nor did I want to take the gun down any further than a field strip. I started using the eraser as an exercise in boredom one day & found that it actually worked. I also hit the striker blocker with the eraser. I noticed it had concentric circle mill marks & while I didn't take those marks off I smoothed them out. A mechanical pencil fits in that narrow space & with lots of rubbing & time it'll start looking smoother & shinier. I might try something a little more abrasive on it but so far any residual grittiness is minimal. And just like you found, the reset is more pronounced both audible & tactile. Something that simple that only takes a normal field strip & no tools is definitely worth a try. I also activate the sear disconnect & work the trigger a lot which also seems to help. That metal on metal has to be wearing everything smooth.

Along with lots of shooting & ammo expenditure I'm sure it'll be completely grit-free in a short time. If it gets no better than what it is right now I'll be satisfied.

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Former USN, Retired US Army

A picture of where you smoothed would be priceless!!!

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Kirk / Spock 2020

Did the same to mine when I bought it. The easiest enhancement to smooth operation.

Sent from my Nexus 7 using Tapatalk now Free

A common "fix" for the gritty feel.

Apex gritty.

That's the spot; pic attached.

1000-grit cuts very lightly and so long as you keep it flat and parallel to the face you're working on, there's very little chance of removing too much material.

Attached Images

SBA-Face.jpg (46.7 KB, 409 views)

I just looked at mine under a jeweler's loop and it isn't very smooth at all. I can see ridges the USB rides on and wears on.

I'm going to polish the USB bore and that trigger bar and report back.

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Kirk / Spock 2020

In the length of a TV show, with some elbow grease and some metal polish (Mother's mag polish, Flix) you can polish up most all the metal parts. Smooth, not removing material.
If for no other reason, dirt has a harder time sticking to smooth surfaces.

I suggest these steps before removing the rear sight.

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-Ric
Keep Calm and Carry

I did my polishing on a 45c I just bought and created a thread titled "10 minute trigger job" or something like that.

My trigger went from horrible to wonderful! I can't wait to get back out to the farm to rattle off a few hundred rounds. I just sit in the house dry-firing and smiling.

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Kirk / Spock 2020

My Shield trigger was slightly gritty and I was putting off polishing the striker bore because I didn't feel like removing the rear site. I just polished the trigger bar with 600 grit paper; that's what i had laying around and followed with Mother's mag polish as suggested by ric_in_or. What a difference; trigger is smooth as silk

Yep, that part on the trigger bar is the most common culprit. You don't need any magnification to see that it's not smooth. Add to that the fact that the striker block has a sharp corner on it and you get a gritty trigger.

This is why the Apex USB is rounded.

Still, smoothing the trigger bar will resolve most of the grittyness.

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Freedom isn't free.

Nice. I dropped Apex USBs in all of my M&Ps. While it did smooth out the pull, now I'm wondering what effect polishing the contact surface of the trigger bar would have in combination with the Apex striker block...

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The one w/ the gun.

It worked perfectly for me in less than five minutes.

I've put this solution out there several times on this forum. Wonder why it hasn't popped up for people.

This needs to be the 1st action taken on a trigger. Sure would save a lot of hassle trying to modify the USB.

Just some 3M wet/dry paper fixes this quick.