My Son has a S&W M&P AR15 Tactical. He bought a Sparc ll red dot for it & asked me to mount it for him so that it co-witnessed with the flip up sights. Used the supplied riser & bolted it on with good results.
My question is, where on the upper rail should the sight be mounted ? I put it about ½ of the way out. Seems to be about right to me.