FX impact M3 m3 thread pitch size that hold backbone

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Broozer

Broozer

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Sep 15, 2017
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Santa Paula,California, United States
Anyone know the m3 socket head thread pitch size for the screws that fasten the backbone to the action? The ones under the cheek piece. I know the .5 pitch bolts don’t fit. They are a finer thread. I want to replace them with stainless steel since I don’t use the cheek piece and want to prevent corrosion from my cheek sweat.
Thanks
Gabe
5BF33E43-D98E-4A21-B848-91542C8D44EE.jpeg
 
Just run a tap of the same screws as the rest of the 12 that hold that plate down.

And don’t forget to use nickel anti seize on the threads of your stainless fasteners.

Another tip- if you are in and out of your gun a lot, consider using Torx head fasteners on those 12 screws, along with the three that attach the scope rail
 
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I’m sorry, Gabe. I missed that you were referring to the Airmarksman rail, and I use a saber tactical adjustable cheek rest so unsure about the thread pitch on my own Airmarksman backbone. Maybe send AM a message thru Facebook? That should be the same pitch as the rest of the M3’s. On both my impacts I used standard M3 x .5. Maybe because I ordered stainless replacements right from the start of impact ownership I had no problems.
I used stainless Torx head on all the fasteners holding that backbone down
 
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Broozer said:
Anyone know the m3 socket head thread pitch size for the screws that fasten the backbone to the action? The ones under the cheek piece. I know the .5 pitch bolts don’t fit. They are a finer thread. I want to replace them with stainless steel since I don’t use the cheek piece and want to prevent corrosion from my cheek sweat.
Thanks
Gabe
Click to expand...
Doesn’t the introduction of Stainless steel hurt here?
Aluminum, stainless and cheek sweat — a recipe for galvanic corrosion
 
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Heavyopp said:
Doesn’t the introduction of Stainless steel hurt here?
Aluminum, stainless and cheek sweat — a recipe for galvanic corrosion
Click to expand...
Which is another reason to use the nickel anti seize on the threads of the stainless fasteners.

In the AM backbone rail there are 3 different length of screws, with only one of being the shortest. It goes on the left hand side of the gun, in one of the two threaded holes on top of the rear block of the cocking assembly. That is, if you were looking on top of the rail with the rear of the gun to your left, it would be the top screw hole of that rear block
 
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bigHUN said:
I toke my MK2 apart million times and lost two of the M3x0.5 threaded holes in Rear Block exactly "those ones".
I had to re-thread the entire block for helicoil inserts, and these coming in some different materials as well, SST, titanium...
Just FYI if you force those small threads.
Click to expand...
I just helicoil’d 3 thread holes this past week. Very strong thread connection now on those three. I’m half tempted to just helicoil all the holes that the black bar attach to, and never worry about stripping threads again, lol. That’s exactly what I did on the bolts for my transmission Pan on the A518 Torqueflite on my first Gen dodge diesel
 
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Bigragu said:
I just helicoil’d 3 thread holes this past week. Very strong thread connection now on those three. I’m half tempted to just helicoil all the holes that the black bar attach to, and never worry about stripping threads again, lol. That’s exactly what I did on the bolts for my transmission Pan on the A518 Torqueflite on my first Gen dodge diesel
Click to expand...
Naxt time I open my MK2 I will also re-thread all the M3's
 
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Never had a problem with the fine metric thread in aluminum....
I always use a good Torque control screwdriver when I assemble....
torque1.jpg


Also if you are concerned about galvanic activity... check the label on your anti-seize!!
Most contain graphite... this has it own problem with galvanic action!!
So Like I use on my match AR15.. on the barrel-nut, you use a high Molybdenum content grease...
They suggest AreoShell 33
 
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