Ok, now that we are back on target:
Quote Originally Posted by stangfish View Post
Centerline of the windage knob to the centerline of the action.
I agree with JHelmuth that Yobuck's quotes get the big picture.

I would either go with Stangfish's statement, or would guess that the center of the reticle when properly focused and aligned with the target might be the answer, but I have no facts to back up my guess.

I realize this is still an approximation, and that's the best I believe we are going to get.

Think about the following:
Even if you have your scope mounted on a 0 MOA base, the angle (from horizontal) of the light path from the target through the center of the reticle to your eye is at the same angle as if the scope were mounted on a 20 MOA base.

So, the rhetorical questions I would ask are:

1. Is it really the height of the scope above the barrel that is important or is it really the height of the actual light path above the barrel that we should be measuring?

2. If the answer is the light path, then where along that light path do we measure "scope height?

This is a good academic question and discussion, but, at least for me, at some point I accept approximation as "good enough." I don't think I can consistently and deliberately change my POI by .25 MOA, so I have no problem accepting a reasonable "area of probability" in which my bullets will impact the target.