Field Target Tech Channel Episode #7 Optically Centering a Scope

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Xbowsniper

Xbowsniper

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In this episode of Field Target Tech, I describe the adverse effects of bottoming out scope turrets, and how to optically center a Scope.
https://youtu.be/fM8A8eq3en8

TomHolland 
[email protected] 
Assistant Match Director 
Eastern Suffolk Competitive Airgunners Association (ESCAA) Long Island NY escaaclub.com 

Scott Allen interviews Tom Holland in Episode 12 of the Field Target Podcast at
ftpodcast.com
 
Hi Tom,

Thanks again for the video on centering a scope. Per our exchange on another forum, here's a related article I drafted a while back. I too prefer using a V-block. When talking with folks who are trying it for the first time, it seems the most common issue they run into is chasing their tail with the turrets...not really understanding how to adjust each turret to find the center. Hopefully this will help someone...jump to section 1.3 for the relevant part

1.0 Centering methods
Firstly, let’s have a quick introduction to the 3 common methods for centering:
  1. Mirror method – This method involves aligning the reticle with its reflection in a mirror. The caveat is that it assumes the objective bell is perfectly perpendicular to the tube axis.
  2. Counting clicks – This method involves—you guessed it—counting clicks! The idea is locate the turrets’ end stops and then return to the center. The caveat here is that it assumes the mechanics of the scope are perfectly balanced.
  3. V-block method – This method involves resting the scope in a cradle-like device called a V-block. Then what you do is rotate the scope in the V-block until the reticle spins against your background in one spot.
    [/LIST=1]

    Now let’s talk about how to do each one and look at some advantages and disadvantages.


    1.1 Mirror method
    This method is the quickest and easiest of the three. All you need is a strong light and a mirror. 

    Start by setting the magnification to its minimum and the yardage to infinity. Now press the objective bell against the mirror, taking care to hold it firmly against the glass. A bathroom mirror is typically a good choice. The thicker the glass the better because it allows more room for light to enter where you need it, where the scope meets the glass. And since bathrooms are usually well lit, you may not need additional light but if you do, a bright flashlight is a good choice because you can play with the angle the light enters the glass.

    Now look through the scope and you should be able to see two reticles; the actual reticle and its reflection:
    MGalleryItem.php
    reticle and its reflection in a mirror

    Simply twist the turrets until they lie on top of each other.

    Another advantage is that you can also use a small mirror and do it without removing the scope from your rifle. Naturally, this method can only be used on scopes that have an objective bell that is a simple round shape that can be held flat against the mirror. If instead it has a hooded shape, one of the other methods will have to be used.


    1.2 Counting clicks method
    One, two, three, four……………three hundred and thirty!

    Okay, not quite that literal. Rather than counting clicks one by one, count complete turns. That is, start by turning the turret all the way to its end stop in one direction. Take care not to strip it out by going too far. Then count complete turns until you reach the end stop in the other direction, including whatever final partial turn you get. Then simply go back to the halfway point.
    MGalleryItem.php
    counting turret clicks

    Like the mirror method, this technique can be performed without removing the scope from the rifle.


    1.3 V-block method
    Of the 3 methods, I prefer this one because it registers off of the scope tube, same as the scope mounts. I made a V-block of wood but for a quick one-off, a suitably sized cardboard box with a couple of V-shaped cuts will do.
    MGalleryItem.php
    simple V-block made of wood 
    MGalleryItem.php
    scope placed in V-block
    When you are ready to center your scope, clamp the V-block in a vise (or something else sufficiently stationary) and point the scope at a target. I say a target...anything with a grid or pattern that you can use as visual markers is fine.

    What you want to be able to do is spin the scope and have the intersection of the crosshairs to remain in the same place throughout the rotation. Think the spinning propeller of a helicopter. It can be tricky to home in on the center if you start fiddling with both turrets. Instead, take one at a time.

    It doesn't matter which one we start with so let’s just pick the windage. Orient the scope normally and take note where on the X-axis of your target the crosshairs rest. Then rotate the scope 180° and take note again where the crosshairs end up on the X-axis relative to the previous spot. Now adjust the windage turret to an imagined midway point between those two spots.

    Repeat this back and forth until the spot on the X-axis ends up in the same place when you rotate the scope 180°. While you are rotating the scope back and forth, you will probably notice the crosshairs orbiting against your target. You want to ignore that. All you care about right now is the X-axis and where the crosshairs end up left-to-right when the scope is oriented normally versus when it's upside down (rotated 180°). What it does in between those two points is of no interest.

    Once you have the windage fine tuned, now turn your attention to the elevation turret. Same idea except you're now focusing on the Y-axis.

    When you're done, you should be able to rotate the scope 360° and the crosshairs will remain in the same spot on the paper.

    Note: Be sure your scope's parallax (range) is set correctly or you'll drive yourself crazy trying to get the crosshairs to stop orbiting. It's one thing to have a consistent cheek weld when you're holding a rifle, but here you have nothing to help you keep your eye in exactly the same place behind the ocular bell.

    For that reason, if your scope does not have an adjustable parallax, you need to do this process at the range at which its fixed parallax is set...not what it says on the spec sheet (it's a lie!) but at the range where you can bob your head and not have the crosshairs move against your target.
 
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Davemac,

If one cannot optoptically center a Scope with the v block method, then, most likely the scope is damaged. The adjustments to get it to that center SHOULD get it to the optically centered point. If you crank and crank to get the crosshairs to center, and it does not, then the adjusters within the scope are damaged. Also, if you turn the turrets, and there is no resistance and/or clicks, when it clicked before, the scope is damaged due to the erector tube springs falling away between the erector tube and the scope housing.
Usually, without being on a gun, and actually shooting it, could be tough to determine a damaged scope. As I noted in the video,when you look through the scope, if you get a dark or distorted top , or right , or both, then the erector tube within the scope is crushed, and therefore damaged. If you cannot get a clear image from the distances of focus of the specs advertised by the scopes manufacturer, then the scope could be damaged. Before determining this, you have to make sure that the ocular (eye piece) is adjusted properly for your eyes. This is important in setting up a Scope, for if you have someone else adjust the scope for their eyes, it might not work for your eyes. Everyone's different.

Hope this helps,

Tom Holland 
[email protected] 
Assistant Match Director 
Eastern Suffolk Competitive Airgunners Association (ESCAA) Long Island NY escaaclub.com 
 
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Davemac,

To answer you question on my channel as well, the Sportsmatch, and most other mounts can be used on Springers, don't know if the mounts even have that rating on them. Most mounts that have a locating pin or screw, that's goes through the base of the mount, into a hole, or threaded hole on the gun. This prevents the mounts from scooting around.
More importantly, you need a Springer rated scope to go on a Springer, or else even the best mounts and rings will not be able to stop the damage of a non springer rated scope.

Tom Holland 
[email protected] 
Assistant Match Director 
Eastern Suffolk Competitive Airgunners Association (ESCAA) Long Island NY escaaclub.com 
 
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Thanks Tom I appreciate the feed back, here is another question :)I am new to this, just trying to learn, any suggestions will be greatly appreciated.So if I have a scope I suspect not holding Zero (Leupold springer rated), wouldn't it be simple to test by doing the mirror test center it up, go put it on the gun dont touch adjustments and shoot 20-50 rounds through it, and take it off the gun and check it by doing the mirror test and see if the cross hairs moved or not. If they did not move all is good right?? am I missing something ??



thanks
 
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Davemac,

Optically center your scope, using any method, mount it on a gun, and zero it. Optically Centering a Scope is not zeroing it. Zero the scope after you mounted it on whatever gun you intend to mount it on. Shoot it. All projectiles should go through the same hole, or close, depending on the distance. If they don't go through the same hole, and the distance is far, some other things should be looked at first. Check your hold. Springers are very sensitive to that, as well as cheek weld. Wind. It don't take much. Quality pellets that group in that particular gun. Scope mounts that don't move. Then, after that many shots, the point of impact should not change. If it does, check all i mentioned. There is almost no way to tell If the scopes crosshairs are moving on their own. If you keep having to adjust it more and more, after you zero it, particularly in the same direction, it could be an indicator of that. You could recenter it, but being it was zeroed, it would be difficult to determine if it shifted or not. If it is a Leupold scope, their warranties are some of the best.

Hope this sheds some light on the subject 

Tom Holland 
[email protected] 
Assistant Match Director 
Eastern Suffolk Competitive Airgunners Association (ESCAA) Long Island NY escaaclub.com 

 
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Thanks for the tutorial Tom. I did the V block method first. Then I discovered the mirror method. That took all of 1 minute. Much easier than the V block method.

After doing the V block method, the scope was only off by 1.5-2 moa when doing the mirror method. Do you think that's a big discrepancy between the 2 methods?

Which is more accurate?

I made sure to remove the lens cap cover from the objective end of the scope before using the mirror.

Thanks
 
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Trailryder,

There are several methods guys like to use, I use the v block method as I described in my video. I have never used the mirror method, and offhand, couldn't tell you which one is more accurate than the other, if at all. The best way, in my opinion to optically center a Scope, is to use the v block method at the distance you plan on zeroing at. In my case, that will be 30 yds on the nose, and I use a Sightron Slll 10-50x. At 50x, I can get the elliptical movement of the crosshair down to less than a pellet width. Then I'll adjust my mounts, to my shot, and get it within a pellet as well. Then, just a few fine clicks, and you are sighted in. What this guarantees, is that everything is centered, and you don't have to crank a turn or more (which is undesirable) in order to sight in. 1.5-2 MOA is still good, it's still within the realm of a reasonable amount of clicks.
Hope this sheds some light on your question.

Tom Holland 
[email protected] 
Assistant Match Director 
Eastern Suffolk Competitive Airgunners Association (ESCAA) Long Island NY escaaclub.com 
 
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