Reply To: group tracking with mill dot scope
The bisecting line between the scope center and bore center is the important feature for scope cant. The vertical of the crosshair should lie on that bisecting line. And then that’s what you need to hold level (vertical) when you shoot.
Holding the action level does not necessarily mean that the scope is centered above the bore. The easy way to center the scope above the bore is to tip the rifle slightly one way or the other.
Your mounts can be way off center and still work fine as long as your scope is in rotation and you hold the rifle correctly.
I prefer a scope level that mounts on the scope tube and can be adjusted/rotated to line up with the reticle.
Rotate scope in the mounts to get the crosshair lined up with the bore first. Then, use the level to hold it vertical while shooting.
If your 10 yard and 25 yard shots are hitting about where expected, but the 50 yards shots hit right, then you are just holding the gun canted.
If the 10 yards shots hit left, but the 50 yard shots hit right, then your scope is canted in the rings.
Use of the Wheeler system that was mentioned requires some assumptions (usually incorrect). I would definitely NOT use that method on my guns.
Incorrect assumption #1: the scope rings are centered perfectly on the scope rail.
Incorrect assumption #2: the scope cap is perfectly level with respect to the reticle.