I just got my Aimpoint mounted with a new Larue LT150 mount along with a Troy BUIS and I'm trying to understand what the co-witness should look like.
As it is, I'd say I'm co-witnessing in the bottom 1/5 of the Aimpoint, if at all. When the front sight is centered in the rear aperture, I can't see the bottom of the rear sight circle. It just seems like the Aimpoint is sitting way too high, but maybe that's how it's supposed to look?
Anyway, if anyone has a picture of what their co-witness looks like, I'd like to see it.
Here's a picture of my Comp M2 mounted on an ARMS #22M68, looking through a Troy rear BUIS. The lower picture has while lines drawn over the sight picture to divide it in equal thirds. As you can see, the dot and front sight post are on the lower 1/3 line when the front sight post is centered with the rear sight aparture.
This is what I call a lower third co-witness, but I expect that C4iGrant will soon chime in to dispute my claims. We've been over this a hundred times.
In my experience the Larue provides a co-witness somewhere in the lower 1/4 or lower 1/5 like you are seeing. It doesn't really matter either way as long as you are comfortable with the sight picture.