Help with a Mil-Dot Scope

Discussion in 'Optics & Mounts' started by joshfireart, Sep 28, 2010.

  1. joshfireart

    joshfireart New Member

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    ive trying to under stand mill dots and how to use them the Question i have is what power do you set your scope at. I suspect its the lowest power but it dose not say in any of the info ive seen thanks.b
     
  2. Biohazard2

    Biohazard2 Active Member

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    This may help;
    Mil-dots and Minutes-of-angle - From a Technical Perspective
     

  3. mrm14

    mrm14 Active Member

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    Heres a technical page from Primier Reticles. It is primairly explaining the use of their reitcles, however there is some good info here regarding MOA and Mills in this publication. Also in there is some basic info on how mills are used in general for most any mill dot scope.

    http://premierreticles.com/pdfs/2009-HowToGen2.pdf

    When it comes to magnification power of your scope it's pretty much user preference. I, for example, have the Premier Reticles 5-25X56mm scope and I find that I pretty much use the power range of about 16 to 18 to about 600 yards. Beyond 600 yards I may crank up the magnification power to 21 or 22. Not that I'm looking at the power indicator markings on the scope when I'm using it but afterwards thats where the level of magnifications has ended up most of the time. As you increase magnification you will see more of the boils or mirage in the air which can distort the target and its surroundings somewhat. Actually this mirage effect along with reading the wind can aid in determining amount of windage deflection to compensate for, but mostly for those long range shots beyond 600 yards.
     
  4. M14sRock

    M14sRock New Member

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    Are you asking which power to set your scope to, in order to use the mil dots for ranging?

    If so, each SFP (Second Focal Plane) scope has its own setting.

    With an FFP (First Focal Plane) the mil dots work at any magnification.
     
  5. mrm14

    mrm14 Active Member

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  6. IXLR8

    IXLR8 New Member

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    Some scopes, the Nikon comes to mind, have certain setting that makes the mil-dot read correctly. Typically it is in the middle. A 6x-24X scope will have the mill-dot at 12x. That leaves a multiplier of 2 for 6x, and a multiplier of 1/2, for 24x. The standard number is typically denoted with a color different from the other zoom numbers, like the 12x will be red, and others white.

    I bought my first and only FFP scope for my last build, and it was expensive. After using it, I can truly see the value. As a bonus the windage and elevation adjustments were .1mil instead of the customary .25MOA.
     
    Last edited: Oct 19, 2010
  7. M14sRock

    M14sRock New Member

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    Slight correction here, this would be the customary .25MOA, not .25Mil.
     
  8. IXLR8

    IXLR8 New Member

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    You are correct about the MOA, with a standard scope.

    With an FFP scope 3.375 MIL= 1 MOA at any magnification. At low zoom levels the mil-dots are close together. At maximum zoom they are far apart, but still 1 mil at both extremes. However the adjustments are in .1mil increments. This makes adjustments for distance and elevation easier.

    With 2nd FP scope the mil-dots are the same size at every magnification, from the perspective of the shooter. The adjustments are in MOA which change in size depending on the distance.

    With a mil-dot scope distance can be calculated from items of a known size, by counting the dots. Mil-dot scopes were originally only on fixed magnification scopes, which did not pose a scaling problem.

    FYI
    The practical form of this that is easy to remember is: 1 mil at 1 km = 1 metre

    To determine the distance to a target of known size: (Distance in yards) = 1000 / 36 x (Object size in inches) / Mils
     
  9. dave79

    dave79 New Member

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    I recently bought a Tasco 2-6x32 Mildot scope.

    The formula in their instruction sheet has me puzzled. Can anyone comment on why they would suggest to multiply by 333 instead of 1000?

    Instruction sheet:
    (Height in metre x 333) / mils read = Distance in metre

    Everywhere on the web this formula is expressed as:
    (Height x 1000) / mils read = Distance

    It's as if this scope has its dots differently spaced and not like true mildot???

    Anyone?

    Thanks.
     
  10. ccd8541

    ccd8541 New Member

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    I think:

    It is a second focal plane scope and the reticle was designed to be correct at 2x(use the normal ranging formula). At 6x the needed correction is 333(the target gets larger by a value of 3x so they decrease the constant(1000) by 3) .
     
  11. dave79

    dave79 New Member

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    Thanks for the input ccd.

    It's definitely the variety where reticle remain constant regardless of power, so i think second plane.

    I will try again, but from memory i think the 333 multiplier worked on whichever power I used.

    Dave
     
  12. dave79

    dave79 New Member

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    Hi again,

    i've confirmed that 333 works with all power levels.

    using 1000 multiplier results in too great distances.

    so back to the original question: could Tasco NOT be using genuine mildots?

    would this affect holdovers and similar compensating actions?

    dave
     
  13. Highpower

    Highpower New Member

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    The above is just a guess on my part, because I suck at math......

    Which is why I resort to using one of these. :D

    http://www.mildot.com
     
  14. ccd8541

    ccd8541 New Member

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    How have you confirmed it?

    If the reticle is in the second focal plane you can not use the same formula, you are changing the size of the target in relation to the reticle as you adjust the magnification.

    The easiest thing to do is to place a target of a known size downrange and measure it at various magnification settings. EX: 18" target at 100yds. This will tell you what the spacing is.
     
  15. dave79

    dave79 New Member

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    Hey ccd,

    that's exactly how i confirmed, i took a known size object, put known distance away and observed how many mildots at each magnification level, from 2x to 6x.

    plugging in 333 gives correct results.

    increasing power requires dividing the result by appropriate power number, to account for larger picture on the same-size-reticle.

    plugging in 1000 in the equation gives me distances that i know are just too long.

    my comcern now is, unless there is a way to explain why 333 works, then would somehting like 'mildot' card work on my reticle?

    i'm not sure that math will make sense. eg: if the card says compensate by holding-over one dot, and my dot is actually 3x the real mildot? is that possible?

    thanks,
    d.
     
  16. ccd8541

    ccd8541 New Member

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    So, what is the subtension between the dots at the various magnifications?
    If you find a magnification level where the distance between mil-dots is 3.6" at 100yds then all the normal formulas and drop tables will work at that magnification.
     
  17. dave79

    dave79 New Member

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    Firstly, appologies to everyone for hogging the thread with my Tasco scope issue. I think I will just have to consider buying a better scope in the future.

    In reply to ccd, I checked again...

    I took your suggestion that I should see 3.6" @ 100 yards covered by one mildot. Sadly I didn't have so much space so I figured 1/4 of 3.6" at 25 yards should be the same. Let's call that "target area".

    First problem: even at highest magnification (6x) one "mildot" on my reticle covers more than the target area. So this reticle is either faulty, or uses some other standard.

    Of course as I reduce power, the reticle remains the same but target zone shrinks. Maybe if I could magnify more, eventually I would match one dot to the desired target area -- now I wonder if this scope has reticle printed for Tasco's 3-9x (more commonly seen online) but lenses only actually magnify 2-6x?

    So out of curiosity I checked that 333 multiplier again, with known sizes and distances and found that the multiplier is not constant either, as I changed magnification.

    Target size was 6" or 0.15m
    Distance from target was 12.5m
    Solving for multiplier M

    @ 2x (0.15 x M) / 2.75dots = 12.5m
    therefore M = 229

    @ 3x (0.15 x M) / 3.75dots = 12.5m
    therefore M = 312

    @ 4x (0.15 x M) / 5dots = 12.5m
    therefore M = 417

    @ 5x (0.15 x M) / 6.25dots = 12.5m
    therefore M = 520

    So until I can purchase a new scope, I will set this scope to one power level only and learn how to get by. Bit of a bummer but maybe I will learn something accidentaly :)

    Dave.