Updated 4/13- I understand the method below does not account for turret cap angle being off so I tried the method of aligning the reticle to straight egde and adjusting the elevation 200 clicks and then adjusting windage to get back on center if needed. My scope required 4 clicks to return to center so it is about 1.15 degrees of cant. (Tan X = 4/200) Guess the turret caps are straight on my scope
Below are some pics to show how I measured the cant angle in case anyone is interested.
I know it's not the most precise method but I used what I had available and the results are repeatable.
Whould love to hear your comments on the method.
Rifle is clamped in a Tipton gun vise perpendicular (verified) to the target about 25' away.