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Determining Reticle Tick Values At Varying Distances

Discussion in 'Long Gun Accessories and Optics' started by otisrush, Jul 9, 2018.

  1. otisrush

    otisrush Member

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    I know....weird title.....but I struggled to summarize the topic. This is the deal.....

    I have a Vortex HS-T scope - 6-24x. It is a second focal plane scope. So the MOA tick marks on the reticle are only valid when the scope is on 18x.

    I'd like to figure out what those tick marks would equate to (measured in MOA) for various distances at, say, 24x. I'm starting to shoot 1,000 yds on occasion. I'd like to have the scope be on 24x. But if I do so (at least right now) I don't know what those tick marks are measured in MOA.

    Does anyone know if there is a way to figure that out, without actually shooting at 1,000 yds? For example, if I shot at 100 yds and figured out that tick that is 2 MOA on 18x is really 1.7 MOA (or whatever) on 24x, could I then use that same value when shooting at 1,000 yds?

    Thx.

    OR
     
  2. Sistema1927

    Sistema1927 Member

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    Nikon has its SpotOn software (computer and smart phone) for their scopes, I wonder if you can compare yours to one of theirs and do some interpolation. It allows you to adjust for load, weather, magnification, and a bunch of other values.
     
  3. edwardware

    edwardware Member

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    Ask Vortex. They certainly know their own reticle subtensions at different magnifications.

    If you want to figure it out yourself, get a yardstick and a 300 yard range. Should be simple.
     
  4. Varminterror

    Varminterror Member

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    If you can determine the ACTUAL zoom, not just the labeled zoom, then life is VERY simple.

    The math is the same, but I'll start with the easy case.

    Let's say your 6x is truly 6x, and 24x is truly 24x, with the 18x reference truly at 18x. If the hashes are 5MOA apart at 18x, then at 6x, they will be 15MOA apart. Reference Subtension * reference / new zoom = corrected subtension. So 5 moa * 18/6 = 5 *3 = 15MOA. Going the other way, on 24x, 5MOA will cover 3.75MOA, 5 * 18/24 = 3 3/4. I can't recall off of the top, but it seems like the hashes on the Vortex are 5MOA... The math works the same no matter what the subtension.

    If the actual zooms aren't exactly the labeled zooms, then you simply need to develop your scaling by using the reticle to measure a known size object, then remeasure at different zooms. So say you put a 15" target at 100yrds and it measures 3 hash marks on 18x (15MOA), but then on 6x, it doesn't quite fit 1 hash gap, say it's 4/5 of the gap, that would mean your actual low zoom isn't 6x, it's 4.8x. Then you have to make the same ratio correction for all of the other labeled zooms. So instead of using the simplified case ratio corrections I mentioned above, you have to use the TRUE magnifications. So to correct for labeled 6x, you'd multiply by 18 and divide by 4.8, instead of 6.
     
    ATLDave, RussellC, taliv and 4 others like this.
  5. LoonWulf

    LoonWulf Member

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    ^
    Perfect answer

    I just went thru something like this with my Athlon Argos 4-20.
    Its sfp also, and supposed to be "calibrated" for 15x. Unfortunately (or maybe fortunately), theres no 15x marking on the power ring.
    This prompted me to do exactly what VT suggested.
    I set up a grid target at 100yds, marked at 2" 4" 6.2" 8.3". My athlons got 2 moa marks, so that made sense for me. I messed with my power till the little hash marks matched the grid the way i wanted, then marked my power ring. This may not be perfectly accurate, since there is a distance variable using my LRF, and my fitting the reticle to the grid, but its better than just guessing between 14 and 16.
     
    RussellC likes this.
  6. otisrush

    otisrush Member

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    Thanks all. These are very helpful inputs.
     
  7. RussellC

    RussellC Member

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    I was just going to suggest you would have a comment here.....thanks for the input.

    Russellc
     
  8. RussellC

    RussellC Member

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    As an aside, I was reading your posts when you first got that scope with great interest. How are you feeling about it after some use? Sorry for the off topic otisrush, but I figured we are all interested in this stuff....otherwise feel free to respond via PM.

    Thanks, and sorry for the intrusion otisrush...

    Russellc
     
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