M&P9c - Fixing the Thumb Safety (pics)

[BillMans]

I had three changes I wanted to make to the thumb safety on my M&P9c: increase the force required to move the safety to the fire position (more like my Colt 1911), cut off the right side paddle flush with the frame, and cut down the left side paddle width as much as possible. This is an image of the sear assembly and safety lever after removal from the frame, before making any modifications. View is from the left side of the pistol. A pin punch is holding the safety lever and sear assembly together:

The spring loaded "selector" near the center of the image above engages one of the two detents in the safety lever bar; the upper detent is the fire position, and the lower detent is the safe position (as pictured). Notice the detents are shaped like a V-notch, while the selector is rounded. The idea is to file the shape of the notch more like the shape of the selector, which steepens the ridge that must be overcome to switch to the fire position. The needle file I used was elliptical in cross section and tapered:

I used the section of the file about 1 cm from the tip, which is about 0.75mm thick in the shorter dimension. I positioned the sharper side of the file pointing toward the bottom of the V, and pressed the broad rounded side of the file mostly into the ramp of the lower notch leading to the ridge between the notches, trying to avoid deepening the notch. Maybe 5 or so sweeps with the file, then reattached to the assy with the pin punch and tested. I could feel the difference almost immediately, you're not taking a whole lot of material away. Took 6 passes of 5 sweeps. After getting the positive "click" I was looking for, I installed everything in the frame, and found the extra leverage the frame provides left the safety still feeling a little soft, so took it apart and filed a bit more and got it just right.

Then I cut off the right paddle with a dremel, and removed width from the left paddle plastic until I hit metal. I carefully rubbed the part evenly on 80 grit sandpaper, then 600 grit, then polished with a dremel brush:

Finished pistol:

I'm sure I could take a bit more material off the lever, but at this thickness I can no longer feel it when in the holster, so I'm happy with it.

Modify at your own risk, of course.

 

[Rastoff]

This is an excellent instructional post. The pictures are extremely clear and leave no ambiguity on what you did. I'm very impressed and I don't say that very often in threads like this.

I may follow your lead if only to learn how to do this myself.

I'm curious about one thing. Why didn't you grind the right side flat, i.e. no tab at all on the right side?

 

[BillMans]

Thanks for the kind words Rastoff. My thought was to keep dirt out as much as possible in the state in which it will mostly commonly be carried (safe). The tab doesn't protrude outside the frame, but seals up with the slide, sort of:

That said, there are so many gaps between the slide and the frame its probably meaningless.

 

[Rastoff]

I was wondering if that was your thought. I don't know if it will help, but the idea is reasonable. You can't put the frame plug in there so, why not leave something?

 

[scattershot]

Great post. I modified the detent on mine, too, to give it a more positive feel. I would caution anyone trying this to ne careful that the tiny spring that pushes the pin into the detent doesn't fly out. You'll never find it. Don't ask me how I know this.

Also, thanks for the great pics. I have been meaning to do this to my M&P, but wasn't sure where or how much to grind. Very neat modification. I'll do mine the same way.

 

[CBStuard]

Nicely done.