Finding the optical centre of a scope - necessary?

[rf2]

I've obtained a BALVAR 6-24 X 40 scope for a good price as part of a used rifle package. The scope is pretty nice, and it should go well with the rifle, which I plan to use primarily for longer range target shooting. This scope was not installed on the rifle, so I have no idea how it has been adjusted, plus, I've been playing with the turrets.

Anyways, I'm just about ready to mount it on the gun, so I'm wondering if I should go through a procedure I read about that allows you to align the reticle with the optical centre of the scope. Alternatively, I could just mount the scope and bore sight it.

Could anybody tell me about the advantages of aligning the reticle with the optical centre before mounting it and bore sighting it? Or is there some other process I should go through (like just determining the total adjustment range for windage and elevation and placing the reticle in the middle of the adjustment range)?

Thanks in advance for your input.

 

[Aniest]

There are some advantages to the "optical centre" of a scope.

One of them has to do with scopes set for "in use" elevation and windage use (or if you want to adjust them yourself during shooting). In short, in this case you would adjust it to that optical centre and then use adjustable mounts and/or bases that would allow you move them (instead of the scope) for sight in on your ammo: then when you get into the field you can adjust the scope for different windage and elevation knowing that your sight in is at that centre. I have seen a target .338 Lapua set like this: by using the adjustable rings, and adjusting the windage dial (it can be loosened to free spin to a desired spot), when there is no wind at all the rifle shoots perfectly centred left-right when the windage dial is on "0" and thus can be set back to zero at any time without having to remember the setting... and then the elevation dial says "0" but again by using the adjustable bases, and adjusting the elevation dial, the scope is at 1/4 from bottom (in other words, there is 3 or so full turns of "uf" bullet path on the scope) to allow for a large amount of elevation change for long shots.

Optical centre is good to find when the scope itself, bases, receiver base mounting screw holes and/or rings are not aligned or are damaged. I have seen a Ruger .22 with receiver base holes tapped so out of line that only by finding optical centre of the scope and measuring could it be fixed: windage adjustable rings had to be put on to move the Point Of Impact several feet at a distance of only 25 feet.

There are other options/reasons/excuses/points about optical centre... but I would say that unless you want to do it to check the scope and/or mounts for some reason, or if you plan on long shots in high wind, it is probably not needed.

 

[Juster]

One reason for not doing it on elevation is that you are mostly going in one direction for elevation.

 

[Dogleg]

You could find the true optical center, but then what? Nobody has ever given me a good answer for that. Are you going to sight in useing shims? Doubt it.

If you have windage adjustable bases you should get your scope somewhere close to center for windage first, but just counting the total turns from lock to lock then going back halfway is plenty good enough.