Can't adjust sight enough

[Howler]

I just added some Magpul backup sights to the AR I put together. It has a 11" Troy Alpha rail that mounts to the standard barrel nut. My problem is the sights don't line up with the red dot of the scope. The front sight is way low. I've adjusted the post up as far as possible but it's still low. I haven't put a strait edge between the upper and rail yet but I would have to assume the rail has a slope to it. The gap between the upper and rail looks straight. Has this happened to anyone else?

[R1100R]

You should zero the backups by themselves. It has nothing to do with the zero on the red dot.

A lot of times the front sight post is in the lower 1/3 of the glass of the red dot. It depend on the type of red dot mount. Edited December 19, 2014 by R1100R

[gregintenn]

Have you fired the rifle while aiming with the sights?

[Howler]

I figured it out. The angled grip screw was pushing on the bottom of the gas block. This forced the rail in a downward direction. I don't know how I didn't see it when I put it together. After removing the grip the dot and sight post now almost line up.  

[TNMTBik3r]

Glad you fixed it.

My Radical Firearms sights would not zero, the front post was not tall enough (they are Magpul clones). I had to get a different sight set.

[gregintenn]

Simple enough. Glad you found it. Sometimes those type things will drive you nuts til you find them.