Originally Posted by Rickyrebar
...I contacted Leupold's tech line. They suggested that I mechanically center the scope, then check the optical center, "these should be fairly close" according to the tech.
What I found was they were not even close. After optically centering the scope I bore sighted using a Leupold bore sighter, have not been to the range since.
My question / question's...
1. Should the mech. center & optical center be very close?
2. Is it critical that they are? With a "multiple aim point" (Bone & Crocket) reticle, where once its zero'd no adjustments are necessary, how critical would a vast variance between mech. zero & optical zero be?
3. Which would be the more important one to set the scope to, mech. cntr or optic. cntr.?
4. Finally, would having a drastic difference between the two be a clue of internal issues that would warrant sending it to the manufacture for repair?
I know this is a lot to consume but if anyone could school me I would appreciate it.
I think the advice you got from Leupold is odd. You indicated that you have a zero that drifts over time. It seems unlikely the problem is the scope, so why investigate the mechanical center? Unless that model has a history of related problems, it doesn't seem germane.
To answer your questions, the optical and mechanical centers are usually within 5 MOA of each other both vertically and horizontally.
The only exception is when a SFP reticle is vertically offset in the erector tube to increase the elevation range. Then it can be 5-10 MOA away from the vertical mechanical center. When the reticle is correctly offset there should be more bullet up adjustment range than bullet down. If otherwise, then the scope has a problem.
By "optical center", I assume you mean the reticle position when centered with a mirror against the objective.
Which one you should use depends on what you're trying to do. When aligning a scope to the rifle bore (during scope installation), I use the optical center. After the scope is installed, the only thing that really matters is mechanical adjustment range.