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How to center reticle

This is a discussion on How to center reticle within the Long Arm Accessories forums, part of the Rifle & Shotgun Forum category; How do you center the reticle of a scope? Two approaches which I know: I. Put the scope with the objective on a mirror. When ...


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Old April 22nd, 2009, 04:40 AM   #1
 
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How to center reticle

How do you center the reticle of a scope?

Two approaches which I know:
I. Put the scope with the objective on a mirror. When viewing through the scope try to allign the reticle and its image on the mirror.
II. Go to one extreme and count from there the clicks until you reach the other extreme. Half the clicks should be the middle.

Problems I encounterd:
- Both methods do not really get the same result. Guess that the mechanical middle is not the geometrical middle.
- Method I. teaches you what parallax is. It is somewhat a vague method.
- Method II. depends on the scope. My not really low-budget scope, a Leupold VX-III L 3,5-10x56, varies how much you can go in either direction in dependence from where the other is. You see this, when you do the job with a collimator (Boresighter) mounted. So you end up with the question, which middle is the real middle.

Any practical hints? Any experiences?

Thanks,
Fritz



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Old April 22nd, 2009, 03:30 PM   #2
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Fritz, The "count the clicks" method works well but my question is: why are you concerned about centering the reticle? If you use the bayonet type base with the two centering screws, just mechanically center the rear ring and you'll have plenty of windage adjustment to dial in zero. If you use a Weaver, Ruger, or Sako type mounts, there no horizontal adjustment so you get what you get.
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Old April 23rd, 2009, 07:26 PM   #3
 
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Iowegan, with the Burris Signature rings (which don't work for me, yet) or with the method I described elsewhere in the forum to kind of glas bed the scope (which perfectly works for me), you can fully adjust Picatinny rail based mounts.

The basic procedure of what Burris calls "chasing the bullet" is:
- You take a whatsoever mount and sight the scope in. If in this process you end up at the end or nearby the end of the scopes windage, you might consider, using one of the alignment solutions.
- If you go for alignment you have a rational to try and get the scopes reticle centered. And if you have not carefully taken note of what you did on the scopes elevation dials, you understand what I am asking here.
- You put your boresighter on the gun and take note of where the reticle sits. Should be nearby the zero.
- Then you center your scopes reticle.
- Then you "chase the bullet", i.e. you align the reticle, but this time not by the scopes internal adjustments but by either the Burris Signature Pos-Alignment-Inlays or the method I described.

So I see a need to reliably center my scopes reticle.

Fritz
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Old September 2nd, 2009, 08:01 PM   #4
 
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I`ve found that if the adjustments are really out of whack i count the cliks until i get the same number from side to side & top to bottom when checked the last time.

I`m cofused ---wait no i`m not ----maybe LOL

Dang i gotta start looking at the dates !!

Last edited by GP100man; September 2nd, 2009 at 08:03 PM. Reason: addition & spelun
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Old December 15th, 2009, 09:29 AM   #5
 
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i have always used the Count the clicks method and received pretty good results, usually 2 or 3 MOA at 50yds. Gets ya on the paper with a new gun.
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Old December 17th, 2009, 05:33 PM   #6
 
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From Leupold. How to center a reticule

Centering of a scope's adjustment dials
The elevation and windage adjustments of a scope are easily centered. Place the front of the scope against a mirror or place a small mirror against the objective end of the scope. That would be the end farthest from your eye as you look through the scope. Make certain that the mirror is large enough to cover the entire objective. It must also be flat against the objective. With the scope's power selector ring set at the lowest magnification, look through the eyepiece as you would while aiming at a target. If the scope's windage and elevation adjustments are off center, you will see two images of the reticle (cross-hair). To reach the center of the adjustment range, simply turn the elevation and windage dials until you see only one image of the reticle in the center of the scope

Last edited by thomashoward; December 17th, 2009 at 05:35 PM.
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Old December 17th, 2009, 08:42 PM   #7
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thomashoward, The method you described works perfect for optical center but it has its issues. All scopes have a inner tube where the turret screws move the rear of the tube for sight-in. Inexpensive scopes us a rubber "O" ring on the front of the tube to act like a universal joint and allow the rear of the tube to be moved. More expensive scopes have a metal yoke type universal joint in front. There is a flat spring at a 45 degree angle from the turret screws that applies tension on the tube to hold it against the ends of the turret screws. Herein lies the problem. When the scope reticle is optically centered, the inner tube will move farther to right that the left and farther up than down because the flat spring limits travel. So ... what you end up with is 20" adjustment in one direction and 30" in the opposite direction.

When a scope tube is mechanically centered, you have the same number of clicks from center to right and left and the same number from center to top and bottom. When you actually sight the gun in, you will have the same amount of adjustment in all directions, unlike optically centered reticles.

Pre-centering the reticle is a moot point with most scope mounts because the mount itself is fixed so you get what you get .... like a Weaver style, Picatinny, 22 tip-off, dual dovetail, etc. The type of base that uses a dovetail front ring lug and a two set screw rear ring capture is horizontally adjustable. What I normally do with these mounts is to mechanically center the reticle (count clicks) then use my laser bore sighter to adjust the rear capture screws until the vertical crosshair is on the dot. This will get you very close and will have equal clicks in both horizontal directions for correction.

All but some cheapie scopes will have enough adjustment in all directions to sight-in at normal shooting distances. When scopes are used for extreme distances, they run out of vertical movement where the gun won't shoot high enough due to bullet drop. You can then place a shim between the rear ring and the bottom of the scope. This will make the scope tilt down and make the gun shoot higher. For 1000 yard target guns, I have used shims up to .040" thick to get enough vertical adjustment. There are also special bases available for long range shooting designed with a slight downward angle so you don't have to use vertical shims.
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Old December 18th, 2009, 08:52 PM   #8
 
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I like the Burris rings with inserts on my varmint rifles . a "0" on front an a +10 rear give more range. The funny thing is that I did the click count one time and sent the scope to Leupold for a reticule change. They centered it at the factory and said it was 0 and +30 on both windage and elevation. I don't think I was off on the count ,but that's what they said
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Old December 19th, 2009, 03:13 AM   #9
 
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The "count the clicks method" has its drawbacks if the two directions are not independent. This is the case with the Leupold VX-L 3,5-10x56 which I have. Sounds logic if you consider that you center a tube in a tube.

And as thomashoward I have the experience, that I centered my Leupold VX-L 3,5-10x56 (IIRC with the "mirror method") and did send it in for a repair and got it back with the remark, that it had been heavily disadjusted.

Is windage the only reason to get a scope mounted in its optical center?

I don't think so. Getting lenses focus light always is a compromise and the farther you are away from the optical center, the bigger the effects are, just to name chromatic abberation. Thus the manufacturer use apertures. Leupold and Nikon for example do not know how to produce scopes (at a reasonable price at least) and binoculars with comparable optical quality AND the same field of view like Zeiss. Other factors are the apertures to ommit stray light. And then you disadjust these lenses and use the rays from outside the optimal center.

Well at least this sounds reasonable. But even if it is true (what I believe, but I am willed to learn that I am wrong), the question is, wether the difference is to be felt.

Anybody really knows about these issues?

Fritz
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Old December 21st, 2009, 08:24 AM   #10
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Fritz, Although what you say is true about distortion from a "non-centered reticle", it's just something you have to live with. Optical distortion is often the difference between a quality scope and a bargain priced scope.

Here's the point I was trying to get across. Let's say you centered your reticle before mounting the scope. With exception of the dual rear screw bases, no other common mounting system has any adjustment and the dual screw bases are only pre-adjustable for windage.

So .... you attach the base and rings to the gun then mount your scope. Then what? If you want to hit the target, you will have to adjust the turret screws. Do you think the reticle will remain centered after the scope is zeroed? No way! So what's the point of centering the reticle? None, unless you use a dual rear screw base and then only for windage. Here's the challenge: center your reticle, mount your scope, then sight the gun in. Use the mirror technique and check the scope again. I guarantee the reticle will not even be close to center.

The typical mount used on most rifles is not adjustable so you hope the rifle manufacturer drilled the hole for the base properly. Next, you hope the company that made the base also drilled the holes for perfect alignment .... and last, you hope the company that made the rings centered them perfect. I have mounted hundreds of scopes in my time and never once have I seen a fixed base (Weaver style, Picatinny, dual dove tail, etc) where overall alignment was perfect. In other words, the scope turret screws always need to be adjusted and often times, quite a bit.

Nearly all rifle mounts are made where the base is about parallel to the bore. To get the bullet trajectory to intersect with the vertical line of sight, the scope either has to be tilted down a slight amount or you have to adjust the scope's elevation turret screw. The higher the scope is mounted, the more vertical error you will get. Using shims to tilt the scope is a bad idea unless you know how to use tapered shims or use rings with floating inserts. If you use a flat shim in the back ring and no shim in the front ring, you will indeed make the scope tilt down. All is well and good until you tighten the ring screws. Because the front ring is now lower than the back ring, the tube on the scope will bend to conform to the "stair step". This is a good way to ruin a perfectly good scope. Professionals use a tapered set of shims or floating inserts where the scope tilts down but does not "stair step".

Further, the bullets you use can make a considerable difference in windage and elevation adjustment. A barrel with a right twist will make the bullet veer right from bore line and opposite for a left hand twist. The faster the twist rate and/or velocity, the more the bullet will veer. Also, the lower the ballistic coefficient, the more the bullet will veer and the more it will drop. This has been proven time and time again.

Here's an example: I recently sighted my Rem 700 7mm-08 (1:10 RH twist) in with 140 gr Nosler Ballistic Tip bullets (BC=.485) for a dead center POI @ 100 yards ... no wind. My group was very tight and centered on the bullseye. I then fired some Nosler 140 gr hollow points (BC=.323) with the same exact powder charge and virtually identical muzzle velocities. My group with the hollow points was also very tight but it was off to the right a little more than one inch and about a half inch low. I did not touch my scope adjustments or make any changes except the type of bullet. I even confirmed this by shooting some more Ballistic Tip bullets. My groups shifted back to dead center. The hollow point bullet with a lower BC veered right and dropped so what do you do? Easy ... just 5 clicks on the windage turret screw and 2 clicks on the elevation turret screw took care of it. The point is, even if the reticle was perfectly centered for one bullet, it may not be centered for other bullets. I found the same exact phenomenon with many other guns. Depending on what bullets I use (same weight and powder charge) the POI can change as much as a couple inches at 100 yards. That's why turrets are adjustable and why centering the reticle is fruitless!
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Old December 21st, 2009, 09:22 AM   #11
 
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Iowegan- - Thanks once again for your insight. I think we have all had the same experience with different loads changing zero. It seems especially common when shooting 5.56, since there are so many different specs. it's built to, and I think a lot of us have multiple (9 in my case right now) types of ammo, and they perform differently even if all you ever shot was 55 gr. FMJ.

There is one time however when centering your reticle makes a lot of sense: When every gun in your cabinet is cleaned and polished, your ammo is catalogued and stacked neatly, you are bored practicing quick draws in front of a mirror, all is quiet on the Ruger Forum, and you can't keep yourself away from the gunbench!
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Old December 22nd, 2009, 09:14 PM   #12
 
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thomashoward, I like the idea behind the signature rings but have lost confidence in them - admitedly my problem, not neccesaryly corresponding to a quirk of the product ;-)
BTW thanks for the clarification of the mirror method. Had not come across a description in the web. Do you have an URL where this description attributed to Leupold has to be found? Me I never was sure as to the setting of the magnification. Is the lowest setting for ease of use or for maximization of accuracy?

Fritz
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Old December 22nd, 2009, 11:22 PM   #13
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liberalsmakemepuke, I like your second paragraph .... on the boredom meter, centering reticles is second only to organizing your sock drawer .
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Old December 23rd, 2009, 03:12 AM   #14
 
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Iowegan, we here are hunting at night, but electronic night vision devices are strictly forbidden for hunting and shooting. Thus we are somewhat pathologic about getting the very last bit of performance out of our optics.
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Old December 23rd, 2009, 08:05 AM   #15
 
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Quote:
Originally Posted by Fritz View Post
thomashoward, I like the idea behind the signature rings but have lost confidence in them - admitedly my problem, not neccesaryly corresponding to a quirk of the product ;-)
BTW thanks for the clarification of the mirror method. Had not come across a description in the web. Do you have an URL where this description attributed to Leupold has to be found? Me I never was sure as to the setting of the magnification. Is the lowest setting for ease of use or for maximization of accuracy?

Fritz
http://www2.leupold.com/resources/My...ndanswers.aspx
type in: centering reticules and the Q&A will come up

Last edited by thomashoward; December 26th, 2009 at 07:08 PM.
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