Rail shifts from left to right.

[cdj588]

I took my M&P 15T out this weekend and when I went to aim the Troy flip up front sight was crooked (tilted to the left). So I check both the rear and front flip up sights and nothing was wrong. Then, while holding on to my vertical grip I tried to rotate the rail to the right and sure enough it slid to the right about a 1/4 inch. Long story short I got the front post lined up, however I can fairly easily rotate my factory installed quad rail to the left and right.

I am assuming this is not normal nor disirable? I have probably shot 300 rounds through it if that matters at all.

[Iraqgunz]

Are you sure it's the rail and not the barrel? Can you take a picture and show us? You definitely need to get it fixed.


I took my M&P 15T out this weekend and when I went to aim the Troy flip up front sight was crooked (tilted to the left). So I check both the rear and front flip up sights and nothing was wrong. Then, while holding on to my vertical grip I tried to rotate the rail to the right and sure enough it slid to the right about a 1/4 inch. Long story short I got the front post lined up, however I can fairly easily rotate my factory installed quad rail to the left and right.

I am assuming this is not normal nor disirable? I have probably shot 300 rounds through it if that matters at all.

[dennisuello]

Sounds like the barrel nut is loose, unless the four bolts holding that Troy MRF rail on got loose.

[ztf HITMAN]

If it's only the rail, you can look at the Tech Corner section of Troy's website. There is a step by step installation guide on the MRF rail (the one that comes on an M&P15T) Just center the rail, re-tighten the 4 bolts, then re-set the single set screw with blue loctite applied.

[cdj588]

Are you sure it's the rail and not the barrel? Can you take a picture and show us? You definitely need to get it fixed.

I would imagine its the rail since since it isnt touching the barrel and it shifts when I push or pull the vertical grip.

[Stickman]

Tighten it back down and see what happens. You can also pull the screws and check to see if there was any thread locker applied.

[William B.]

I would imagine its the rail since since it isnt touching the barrel and it shifts when I push or pull the vertical grip.

The rail locks on to the barrel nut, though, so if the barrel nut is loose the rail may wobble. I believe that's what Iraqgunz and dennisuello already suggested.