If Trijicon is including both screw lengths with their optics now that is excellent! They used to include a set of 6-32 x 1/2” screws and many a Glock MOS plate was destroyed by people who didn’t realize those screws are too long for their Glocks, which require 6-32 x 3/8” screws.
The longer Trijicon screws (should be 1/2” long) should work fine for the RMR on the M&P. As for plates, I prefer the factory metal plates to anything else, including C&H, but if your factory plates are plastic then the C&H is probably better.
I also generally use the US made alloy steel screws available from McMaster-Carr when mounting RMRs to M&Ps (again, 6-32 x 1/2” with a T15/IP15 torx drive).
The Holosun 407/507/508 optics (For anyone else reading), though using the RMR footprint, require a thinner head diameter so I use the stainless 6-32 x 1/2” screws (T10/IP10 drive) from McMaster-Carr for those.
This is my procedure:
1. Confirm the optic is functional (Use a Duracell battery - they are absolutely better. I conducted a test that lasted around a year and a half using eight Aimpoint H2 optics and various batteries.)
2. Test fit everything to make sure the plate fits the slide, the optic fits the plate, the screws fit and don’t bottom out, etc.
3. Degrease (almost) everything. Use Gun Scrubber, acetone, or I use isopropyl alcohol wipes with toothpicks to get them into the threaded holes. Make sure you degrease the plate, cut in the slide, screws, and screw holes. I prefer a sealing plate for Glock MOS and the M&P factory plates, but you can generally get by without on the M&P if you’re not submerging the optic. If you use one, degrease it. Don’t degrease the bottom of the RMR because you want the O-ring to work.
5. Apply Threadlocker to the screws. Some come with a threadlocker applied but I never trust it fully. I’ll remove what I can then re-apply Loctite 248 paste to about the bottom 3rd of the threads.
6. Torque to spec. The spec depends on the optic and the interacting components such as plates and the pistol itself. S&W specs 15in/lbs, Trijicon is 14-15 (I use 15), and since the plates aren’t threaded I don’t have to worry about them. I always use 15in/lbs on good torque wrenches. I have a few sets of Fix-It-Sticks and a variable Vortex driver. Never use a torque wrench to loosen a screw… only to tighten them down.
7. Take a paint pen and dab a small “puddle” of paint on the alcohol pad wrapper I used. Then I take the point of the toothpick I used to degrease the screw holes, dip it in the paint, and put a thin line from the center of the screw across the radius and onto the body of the optic. That way you get (hopefully) an early warning if something goes wrong, and it’s something you can easily inspect prior to carry.
8. Wait 24 hours prior to shooting.
9. Once the pistol is zeroed, you may want to mark the windage and elevation dials and optic body as well… I’ve heard of them moving but never experienced it myself.
I’ve done a couple hundred M&Ps myself and other armorers have done a couple hundred more this way and it’s worked VERY well. Gunsite has adopted this method also.
