On the S&W M&P15 ORC (Optics Ready Carbine) is the gas block rail a Weaver rail or Pikitinny??

I bought a TruGlo removable front sight (Model TG115) to use a back up to my red dot scope. It says it will fit both Pik. and Weaver AR15 gas block rails, but it is not going on the M&P15. Any idea why??

Here's a link to the item I bought: http://www.midwayusa.com/viewproduct...tnumber=938682

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Pete T.

hey.
i see your in CT too. im near the casinos.

but to our question, i just got my gun today and put a brownel front sight on it. i cant see the bottom of the sight you bought, but is there one rung kinda deal on the bottom or two?