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The shoe-box for testing center line

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/31/2008 at 02:32
8shots View Drop Down
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This forum, and others, have often advised that the center point of a scope can be found by using a shoebox. Cut a V on each side of the open side, place your scope in it and roll it 90 deg at a time. The cross or center point should remain on the same aiming point. If not, one can adjust the vertical and horizontal lines untill it is so. Alternatively, when fitting a new scope, set the vertical line center by this method. The mount the scope and use the mounting windage screws to alighn the vertical line with the bore.
Well, the principle is sound, but not the shoebox. I tried it this week-end and found that a much sturdier thing then a shoebox is required. (Like your wifes favourite tupperware container).
A shoebox is to flimsy and moves during the rotating process. A thou of an inch is enough to throw you. Maybe if you filled it with sand to support the sides??
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/31/2008 at 17:35
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X = 180 Y = 90 (X+Pyro)+(Y-Pyro) = ?

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Call me a newbie, but I don't understand the purpose of this? I use talley lightweight mounts, does this apply to me? I just take a scope out of the box, put it in the rings and bore sight it. Is this wrong?
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/31/2008 at 20:57
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I'm not a big "bore-sight" fan.  For bolt actions, I just remove the bolt and look down the barrel and line it up with a target and then adjust the scope to the target..... works great every time! 
 
As far as what 8shots is talking about..... I have never heard of that!


Edited by Tip69 - March/31/2008 at 20:58
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/31/2008 at 22:32
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X = 180 Y = 90 (X+Pyro)+(Y-Pyro) = ?

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Tip, I believe the process you refer to is basically bore sighting without having to use equipment? Have done it this way myself. Had good results.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/31/2008 at 23:10
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What 8shots is doing is trying to find the center of the scope. If the scope windage or elevation is not centered it is harder to mount the scope where the cross hair is in the center (sweet spot) of the scope. by rotating the scope and watching the arc of the center the center of the scope can be found. The center may not be the count from side to side divided.

Edited by 3_tens - March/31/2008 at 23:13
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/31/2008 at 23:14
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Have to admit I've never had this problem mounting a new scope. I'll pick-up a new pair of shoes tomorrow just in case though........grin
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/01/2008 at 03:20
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The process I am referring to is to firstly find the true center of your scope reticule. This can be done by counting the number of clicks by dialing the scope adjustment from the one end to the other. Say yo get 100 clicks. Divide by two and count 50 clicks. Theoretically your reticule is now in the center. In order to check if this is indeed so, you have to look at an aiming point through the scope. By rotating the scope 90 degrees at a time, through a 360 deg, the reticule should not move off of the aiming point.
The method for turning the scope is often recommended as using a shoe box with two V's cut in it to hold the scope while you are turning it.
The purpose of this thread was simply to say a shoe-box is to flimsy and moves to much whilst turning the scope.
When mounting a scope for the first time, the reticule should be checked that it is centered, particularly the vertical line or windage. This is so that when you mount the scope and boreight it, that the reticule does not end up being maxed out to the left or right. One centers the crosshair, either by counting the clicks, or using the rotating method. Then you mount the scope, and if the scope mounts pemit you to move windage, you do so with the scope mount screws, not the scope windage dials. This would ensure that your scope reticule is in the center of its adjustment after sighting in.
The elevation is a bit different, as very few mounts allow elevation adjustment. So after mounting you can only use the elevation scope dial to find zero.
What is the purpose of all of this? Very little if you don't care other then that your bullet hits where you aim. For the more particular and the target shooters, this type of zeroing ensures the best stress free type of setting your scope. In other words the dials and springs etc are in the best position for repeatable performance.


Edited by 8shots - April/01/2008 at 04:02
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/01/2008 at 03:24
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Originally posted by Tip69 Tip69 wrote:

I'm not a big "bore-sight" fan.  For bolt actions, I just remove the bolt and look down the barrel and line it up with a target and then adjust the scope to the target..... works great every time! 
 
As far as what 8shots is talking about..... I have never heard of that!
 
Tip69, the process you describe here is "bore-sighting".
 
The process I am describing has nothing to do with zeroing your scope. It is a process to find the exact center of your scope.
 
Yes, it is wrong to just take a scope out of the box and mount it. First check that the reticule is at least more or less centered by counting the clicks.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/01/2008 at 03:29
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Originally posted by trigger29 trigger29 wrote:

Tip, I believe the process you refer to is basically bore sighting without having to use equipment? Have done it this way myself. Had good results.
 
After finding the center, I also place the scope on the rifle and then bore-sight it by looking through the barrel. For windage I adjust the scope mounts, for elevation I dial the scope dials.
 
On my last sighting in my windage was spot on and I never touched the windage scope dials. I only had to adjust elevation. I know that I have a scope mouted with very little stress on the dials, as the reticules are well centered by doing a pre-installation check. Will I shoot any better? Probably not!
 
You can see the 4 shots for sighting in started vertically in line from the mounting process. I never touched my windage dials during sighting in. First one on very top of paper.
 


Edited by 8shots - April/01/2008 at 04:10
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/01/2008 at 09:44
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This is a good idea. I recently mounted an old Redfield scope on a 30-30 that didn't have windage clicks. You could completely unscrew and remove the guts out of the turrett if you wanted to. So, leaving the adjustment in the center was a wild guess at best. I didn't use the shoe box. I used my gun vice and left the rings just loose enough that I could still turn the scope - and the corner of a brick wall for reference. Once I knew I was centered, I tightened the rings up and bore sighted with a laser using the windage screws on the mounts. Now I know I'm in the center with maximum adjustment left in the scope.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/01/2008 at 11:44
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Geez........ does this mean I have to go and un-mount all my scopes and do the shoe-box test?  They all seem to work ok at 100 yds...... I still need to shoot a few at 200 yds...... but at 100 they are spot on!
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/01/2008 at 12:46
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I learned a technique from a Leupold staffer, it uses a small mirror and your unmounted scope.

Lay the mirror flat on a table, then stand the scope upright on the mirror with the objective lens down. Look down the scope from the ocular lens end, and you will see the crosshair and a second image of the crosshair. When the crosshair is centered in the scope, they will coincide.

If not, turn the elevation and windage adjustments to make it so.

jim
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/01/2008 at 13:38
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the mirror trick is what my dad told me to do years ago
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/02/2008 at 03:25
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Originally posted by Tip69 Tip69 wrote:

Geez........ does this mean I have to go and un-mount all my scopes and do the shoe-box test?  They all seem to work ok at 100 yds...... I still need to shoot a few at 200 yds...... but at 100 they are spot on!
 
No you need not un-mount your scopes. If they are good at 100yds they will be good further out.
It may however be that your vertical reticule is off-center. The negative effect of this is that if it is badly off-center you may have:
Increased parallax error due to struggling to maintain proper centering of your eye with the center of the scope.
Erratic scope adjustment, for example if you move 6 clicks down, the POI may also shift left or right.
Scope turret spring fatigue after a couple of years, which may effect reliability.
 
You can check your scopes without un-mounting your scopes. Count the clicks to the left, write it down so you won't forget. Count the clicks all the way to the right. It should be about double the amount you went left. Then go all the way left and count the same clicks right as your first count left. This should bring you back to your original starting point.
If you get much more or less then double, you are off-center and may want to correct this.
 
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/02/2008 at 07:23
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8shots is correct.  Years ago after doing a lot of reading regarding the proper installation of a rifle scope, I ran across an article that stated you should make sure the reticle is properly centered in the scope for the reasons he states above.  The cardboard box test was recommended.  Just rotate the scope and make sure the cross hairs remainn centered, if not adjust so that they are.  Apparently many scopes from the factory were not centered.  After trying this on many scopes, finding most modern scopes to be pretty much on the money, I have abandoned the process.  You can do the same thing in the scope rings on the rifle, if you wish for a sturdier surface.  I might just try it again next time I mount a scope.  The mirror trick should work fine, as long as the objective is perfectly flat, as well as the mirror.  Rotating the scope in a set of rings averages out in potential problems with any inconsistent concentricity of the tube of the scope.

Edited by Dolphin - April/02/2008 at 07:26
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