Optically centering a scope is a pretty easy process, it involves centering the reticle back to the point to its factory setting. You are essentially resetting the scope to its default setting. The reasons to do this are varied, but essentially it’s something I suggest anyone do before they attempt to zero an optic.
Why Would I Want To Center My Optic?
Centering an optic is important if you tend to run one scope over several platforms. Different calibers and different rifles with different barrel lengths or muzzle devices can affect how the weapon is zeroed and this can cause a varying degree of adjustments between weapons.
You may also want to center your optic if you are running out of elevation and windage adjustments as you attempt to zero the weapon, or make adjustments for longer ranges. When you center an optic you maximize the amount of adjustments you can make. The more adjustments you can make the farther you can shoot, and the more precise you can be.
Also you may want to optically center your scope if you are dealing with the following issues:
-Your optic will not hold zero.
-You are getting major adjustments for minor turret adjustments.
-Your reticle is “jumping”
Pick Your Method
There are two methods you can use to optically center a scope, the Mirror method, and the Counting method. Both are simple and easy to do.
Before we go over the methods the first step is unmounting your scope from your rifle. You’ll have to zero the weapon and optic regardless, it’s much easier to optically center the scope that way, and is also safer, and the only way to verify your scope is optically centered.
To use the mirror method, you’ll need a mirror, of course and a well-lit room. The mirror method does not work well with optics like a Trijicon ACOG with an illuminated reticle that is permanently turned on. The illumination will reflect and make things very difficult.
If your scope has a fixed sunshade you’ll need to use a lens cover that can open. If the sunshade can be removed go ahead and do so. You’ll need to set the scope flush against the mirror to maximize the efficiency. Once the scope is set against the mirror look through the scope and observe your crosshairs. If your scope has a centered reticle all you will see is the reticle itself. If it is not optically centered you’ll see a shadow of your reticle in the reflection.
Your goal is to line this shadow reticle up with the actual reticle. You’ll do this by making adjustments with the elevation and windage turrets. You’ll simply adjust the turrets until the shadow reticle disappears into the actual reticle. Once you’ve done that, your optic is now optically centered.
The counting method takes a little more time, but can done anywhere, in the dark, and a mirror free environment. The counting method involves you spinning the elevation and windage one at a time. It doesn’t matter which you do first but fully center either elevation or windage first. It’s simply much easier to do one at a time. You want to spin the turrets to as far as possible in one direction. Do not overturn the turrets! Once you begin to feel resistance on your turret go ahead and stop. Now slowly, begin turning that same turret in the opposite direction, counting the clicks as you turn back.
Now once you reach that end of that rotation take the clicks you counted, let’s say it was 52 clicks. Divide that number half, so now you have 26, these now rotate the turret in the same direction you did the first time. However, only do it for 26 clicks. On your 26th click, you are optically centered.
An Important Note
While we call it Optically centering, it’s not going to be as precise as what the factory does. This is an approximation of optical centering. To truly optically center your scope you need some expensive optics gear. However, this is the closest method you can do at home, and in the field even.
Taking time to optically center your scope is an important step in zeroing your rifle. Taking the ten minutes to do so can save you a lot of time frustration when it comes time to get your rifle ready and zeroed.