Objective way to level crosshair

Discussion in 'Long Range Scopes and Other Optics' started by MOA, Jun 3, 2004.

  1. MOA

    MOA Well-Known Member

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    I have mounted many scopes in my lifetime and have used various methods to level my scope's crosshairs. I have found that the best method is to hang a string with a heavy object and use that as vertical. This method is far from perfect but has always satisfied me since I just click in the elevation. Now I have a NPR2 and I use the vertical crosshair for elevation instead of clicking in. I cannot imagine the amount of error that can be introduced if the crosshair is not exactly vertical. I'd like to hear from those of you who have a fool-proof method of leveling the reticle.
     
  2. Michael Eichele

    Michael Eichele Well-Known Member

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    Personaly, I use an actual level. I set up the rifle and using the rear mounting base, I lay a high quality topedo level accross the base and level the rifle. Next I attach the scope (I use QR rings) then I lay the level accross the turret. I then make the needed adjustments. As I tighten the rings around the scope, it turns so I have to tighten 1 side a little, and then the other, all the while I watch the level. Once that is done I install and level a anti cant device.

    I am sure this method is not "fool proof" but it has always worked VERY well for me. out to 600 yards I get NO left to right drift with the clicks or by using hold overs. Out to 1K I get drift to the right. I would imagine that is a function of spin drift and/or coroilus.
     
  3. MOA

    MOA Well-Known Member

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    Michael,
    Thanks for the reply but I was looking for a little more precision. I have plenty of levels lying around. The problem is that we are talking about 1 and 2 degree (and hopefeully less)differneces--a level just doesn't cut it. More suggestions??
     
  4. Dave King

    Dave King Well-Known Member

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    Use a plumb bob on a large distant backer (200 yards should do) to establish true vertical. Establish three aiming points along the previously established true vertical line, the distance between these aimpoint should be as large as possible (limited by the elevation available internal to the scope mechanism). Using your 200 yard zero (assume the backer is at 200 yards) fire onto the center point of aim, then adjust the scope up about 12 MOA or more (24" at 200 yards) and fire another group onto the backer using the upper previously extablisted point of aim, lastly adjust the scope to 12 MOA below the inital group and shoot again. Plot the center(s) of these groups, if they aren't tracking plumb you'll need to adjust the scope/rifle combination to establish true vertical.

    You may find that the reticle is not installed exactly parallel with the elevation mechanism, I could imagine a few degrees of allowable error.

    I suppose a person could check for mis-alignment between the mechanism(s) and the reticle by capturing the scope or rifle/scope combination in a vise and tracking the apparent movement of the reticle against a distance plumb line. Set the reticle vertical line to match the plumb line then adjust the elevation mechanism from top to bottom and watch to see if it diverges from true plumb/vertical.


    Something I have not tried yet. Set the rifle on a bench and place the center of the muzzle directly against a plumb line which extends downward from a support far above the bench. Viewing through the scope this plumb line will probably be nearly invisible and somewhat useless BUT if a mirror were place at a considerable distance from the rifle and the observer used the reflection of the rifle and plumb line in the mirror to check plumb it may be possible to see if the rifle/scope combination is canted. Far fetched but something I may try some day.
     
  5. Michael Eichele

    Michael Eichele Well-Known Member

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    If you havnt tried it, you might be suprised. With 100 click and no side drift, I would say there is under 1 degree of cant. It takes 1 or more to notice.

    The string method is nice, but you still need to make sure the rifle itself is level before leveling the scope. The only logical way to do that is...a level. If your level is not true and you use the string method, your scope is not level. If you use a level on the rifle and the same level on the scope, it does not matter if the level is true or not as long as the bubble used on the rifle is in the exact same position as when used on the scope. Then you know that the scope is 90 degrees with the rifle. From there, if you dont use and ACD, you are wasting your time anyway.

    Regards

    [ 06-05-2004: Message edited by: meichele ]
     
  6. redshanks

    redshanks Member

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  7. redshanks

    redshanks Member

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    Double post

    [ 06-05-2004: Message edited by: redshanks ]
     
  8. ralfus

    ralfus Active Member

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    A lot of folks worry about leveling their scope without wondering if the rifle is level.
    This comes in handy - Magnetic Angle Finder It's not expensive at $5. You can place a straight edge across the base(s) under the scope and make sure the rifle is level and then put the level on the top turret. There may still be some error in the erector assembly but it will get you close. The angle finder listed makes it rather easy to read 1/2 or even 1/4 degree errors. the needle bounces a little but will dampen after a few seconds. Another way to compare is to level across the base prior to scope mounting and compare level to the front or rear sight bases. If they are the same then you can us the sight base to compare level to the scope once its mounted.

    Edited to add: I just realized that I resurrected a 5 year old thread.
     
  9. fj40mojo

    fj40mojo Well-Known Member

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    I found my old post and copied and pasted this.

    My ideology here is that the goal is to align the reticle vertically with the bore. I find a machined surface somewhere on the bottom of the action (whether that is the recoil lug or the actual bottom of the action) and use a precision ground block to support the action. This means that my action is now in a parallel attitude with my reference surface. Then I'm using a precision ground tool (square) to establish a vertical line from the same reference surface that I then align the vertical crosshair with. Everything is referenced off of the same surface and a machined surface of the action. It works for me, and as a machinist it makes sense to me to use the same techniques an inspector would use. If I had a 100yard long granite surface plate I would use that, but to my knowlege no one has one of those. It's not as complicated as it sounds and the tools are inexpensive and accurate.
     
  10. ralfus

    ralfus Active Member

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    Good idea. I've removed the stock and it works well on a Mauser or winchester 70 but on a round receiver your only assuming the recoil lug is machined square and level on its bottom surface and wasn't canted when the barrel was torqued. I like your idea of using a square as a vertical reference. I'll have to try that.
     
  11. fj40mojo

    fj40mojo Well-Known Member

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    I've had to use the recoil lug only on Rem 700s and Model 7s, and it worked fine. All my other bolt guns have some sort of machined flat surface on the bottom of the receiver that provides a good reference.
     
  12. jerrschmitt

    jerrschmitt Well-Known Member

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    I level my rifle first with a small level then I level the scope with a plumb bob but none of that is final proof. I go to the range and sight in the rifle and then raise the elevation knob 20 or so min and see if I have a pumb line from that group to the first group. If not, somethng is out of plumb.
     
  13. Forester

    Forester Well-Known Member

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    +1

    All the versions of eyeballing it leave a degree of imperfection, get it close this way and then go to the range and shoot, if it tracks straight, or in the case of the OP holds over straight then it is straight. Its the ONLY way to be certain.
     
  14. fj40mojo

    fj40mojo Well-Known Member

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    Yes, this is for initial set up. Nothing will replace actual at the range verification of true plumb by shooting "the box".