Question about zeroing.

Discussion in 'Long Range Scopes and Other Optics' started by phillietimothy, Jan 15, 2011.

  1. phillietimothy

    phillietimothy Well-Known Member

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    Gentlemen,

    Hello all. I am watching long Range Pursuit, the gentleman from Gunwerks was zeroing at 700 yards. He stated his group was 1 moa low, am I correct in assuming that he was 7" low? Also, with your indulgence; how can he be sure that after adjusting 4 clicks(1/4 moa) up, that dialing 950 on his turret would work for 950 yards? Trajectory doesn't change in equal increments. By the way the shot was on at 950 yards. I am assuming his 4 click adjustment had him dead on at 700 yards, but I don't see how dialing a particular range on a dial can be predictable unless trajectory changed an equal amount between different ranges. Please help, everytime I think I'm understanding, I'm back to square 1. Thank you, I hope this is the right spot for questions.

    Tim
     
  2. J E Custom

    J E Custom Well-Known Member

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    He may have a set of calibrated turret caps that are for his load.

    Under normal conditions (The conditions that he developed his drop chart under) they would
    be very close. and this would be the reason that he was Off by 1 MOA (Conditions were different).

    So with the new/current conditions all he would need to do is look at his drop chart and the setting
    for 950 yards and add 1 MOA to that for the correct POI.

    J E CUSTOM
     

  3. Buffalobob

    Buffalobob Writers Guild

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    To put it a different way, a person is foolish to not have confirmed at some point in time that their ballistic chart is accurate by actually shooting it in at known ranges.

    So if he just arrived at the range and shot at 700 yards and found himself 1 MOA low or 7 inches he would know exactly what to do to be dead zero at some other distance. This is exactly what we all do at F-class or long range benchrest. We have what is known as "sighters". So we dial up our scopes to 800 yards or 1000 yards as the case may be and take a few shots and see how the current conditions are affecting our ballistics and then we compensate to get it to exactly zero and are GTG for the rest of the way at any other distance.
     
  4. davewilson

    davewilson Well-Known Member

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    this is just one of several things that make a first shot hit at distance very difficult.
     
  5. phillietimothy

    phillietimothy Well-Known Member

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    Thank you JE Custom and Buffalobob. I appreciate your response and your time. I understand the concept of verification by shooting and ballistic matching/cartridge specific turrets. The dial on the turrets appeared to have markings uniformly spaced. The 1/4 moa clicks have to be consistent and repeatable. Bullet trajectory does not change consistently between different ranges. For instance bullet drop between 500 - 600 yards would be flatter than say between 700 and 800 yards. How can dialing different ranges reflect that? In a controlled environment, if I am zeroed for 500 yards(point of aim/point of impact converge) If I simply turn the dial to 6,7, or 8(changing point of aim) if I am on at 600, 700, and 800 yards, that would mean the bullet drop between 500-600, 600-700, and 700-800 would be exactly the same. I think I am confused about clicks and dialing perhaps, I do grasp that choosing an appropiate zero and cartridge for your intended application goes a long way to dial in success. I am trying to be overly descriptive in hopes that some of you can see where I'm misunderstanding.
     
  6. eyeballjr

    eyeballjr Well-Known Member

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    On a custom turret, the spacing between the yardage numbers are not the same. They are spaced out according the the amount of clicks it takes to get from each yardage mark. So it might be 10 clicks between 5 and 600 yards while between 6 and 7 might be 12 clicks and so forth.
     
  7. phillietimothy

    phillietimothy Well-Known Member

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    Eyeballjr,

    Thank you very much, that makes sense. So my thinking was correct, I did not know the markings were spaced to coincide with the cartridge specific trajectory. JE Custom mentioned this as well, would I be correct in assuming that the space on the dial between 4-5 would be smaller than the space between 7-8? I am assuming that caliber x has a flatter trajectory between 400 - 500 yards than between 700 - 800 yards. The knowledge and willingness to share on this sight is phenomenal. I know that the continued existence of the shooting sports is dependent on encouraging and helping new shooters. Well done.
     
  8. eyeballjr

    eyeballjr Well-Known Member

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    You would be correct in thinking that. Essentially it is like taking a target turret and sighting in at lets say 100 yards, taking a piece of tape and wrapping around the turret and making a mark, finding how many clicks it take to get to 200 yards and make a mark. 300 mark,400 mark and so on. It just looks a lot neater when it is laser engraved on the turret than when you just do it on a piece of tape or something.