Quad rail fail!!!?

[Medicsam]

So I just try to have a new take off quad rail from a DPMS SASS .308 onto my M&P 10 and the barrel nut was too small. Can anybody tell me why this is? I'm almost positive that my rifle takes DPMS parts right?

 

[mcap1655]

Yes - the barrel nut is a DPMS LR-308 style nut. At least it is on mine...DPMS have a 1 7/16"-16 pitch and Armalite/Noveske uppers have a 1 7/16"-18 pitch thread.

If the threads on your current barrel nut are too fine - it sounds like an Armalite pattern. Armalite pattern will go on a few threads and tighten up. Your barrel nut should easily go all the way to the receiver.