MilDot scope zeroed at 100 metres no 100 yards.

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  • MilDot scope zeroed at 100 metres no 100 yards.

    Guys wanted to get your thoughts on the effect of zeroing a MilDot reticle at 100 metres not 100 yards as is stipulated in most manuals in order to use its BDC capability.
    As most ranges here in Aus use metre increments, I've zeroed my .308 at the 100m distance. Considering that 100m = 109 yards it doesn't really seem that greater issue however, once you start pushing out to 400m (437y), 500m (546y) and 600m (656y) will this effect the ability to use the MilDots successfully?

    Food for thought.

  • #2
    If it is a true mildot. (Check to see what magnification is the true calibration, normally 10x)
    Then you are better off working in meters anyway because 1 MiliRadian (mildot) = 100mm @ 100M, 200mm @ 200M etc,
    You can work in Yards too but it is not as simple.
    Essentially, at a true Mildot calibration like 10x magnification, the distance between each dot is 1/1000th of the distance, so even in yards 1 Mill at 1000 yards = 1Yard but it gets tricky at other distances - 850yds = 30.6"........Not so easy to work out in your head (850yds x 36" divided by 1000)

    BDC Retcules are not actually MilRadians so you need to confim which it is.
    Does the gap between them get larger the further you go down the scale? That is a BDC reticule.
    Mildots are all the same spacing.

    Now for Mil dot scopes.
    Radians are a measure of angle just like degrees except there are 2 Pye Radians (2x Pye = 6.283 Radians) in 360 degrees (full circle) so 1 MiliRadian is 1/1000th of a Radian which is also equal to 3.436 Moa. (call it 3.45 for ease)

    Of course all this is erelivant if your scope is a SFP & you are using it on a magnification other than that which it is calibrated to.

    If that is the case you need to factor in the magnification.

    Basic formulae for ranging with milradians.

    Distance (m) = Height of target (mm) divided by Mils.

    Now you can transpose that so you can use it for holdover.

    Holdover (Mills or No, of dots) = Height (drop in mm) divided by Distance (m)

    Now if your using a 9x scope with a true MilRadian calibration of 10x. you can factor in the difference in magnification for a SFP scope.

    You just multiply the height figure by the Mag /10

    As in Holdover = (height x 0.9) divided by distance.

    Transpose it again & we can see that a 9x scope is not actually 100mm @ 100m

    H = Dist / Dots x .9
    H = 111mm @ 100m (call it 110mm)

    Same goes if your using 16x with a 10x calibrated scope. Just multiply the Height figure by 1.6

    Cheers, Mick.

    Comment


    • #3
      ?
      Isn't that the whole point of MilDot? If you zero in m work in m, if you zero in yards work in yards? Don't try to zero in m and then work in yards or the other way around. For your drops unless you are good at the conversions.
      You can use the rec to estimate the distance to the target if you know the size of the target.
      e.g. 2m tall target board measures four MilDots in the scope then it is 500m away from you provided your scope is either FFP or if SFP it's at the correct zoom setting.

      1ft long rabbit takes up 2 MilDots in your scope, that rabbit is 500ft away from you provided the scope is FFP or if it's SFP it's at the correct zoom setting.

      Comment


      • Guest's Avatar
        Guest commented
        Editing a comment
        use a ballistic app/calculator such as Strelock there are some great apps to look at to help with working out range estimation, and target size etc etc. i use istrelock on the iphone just for playing around but out in the field if you all set up you can accurately compensate for wind and drop. there are specific mildot applications that will run through mil dot use as well. I had a look but i dont own a mildot scope so it was more for info rather than actually trying it out. iStrelock will utilise the reticle subtensions and recalculate for different magnifications too and this one works well with any reticle that is listed except for a duplex style. new reticles are being added all the time as well. Good luck it looks complex but im sure like anything it is easy when you know how.

    • #4
      Originally posted by Cannon" post=41866
      Guys wanted to get your thoughts on the effect of zeroing a MilDot reticle at 100 metres not 100 yards as is stipulated in most manuals in order to use its BDC capability.
      As most ranges here in Aus use metre increments, I've zeroed my .308 at the 100m distance. Considering that 100m = 109 yards it doesn't really seem that greater issue however, once you start pushing out to 400m (437y), 500m (546y) and 600m (656y) will this effect the ability to use the MilDots successfully?

      Food for thought.
      Is your BDC a turret cam BDC or reticule?

      Comment


      • #5
        Hey guys, sorry to confuse you.
        Mick I think you misunderstood me mate. Its definitely a MilDot (Vortex viper 6.5-20x50). I was trying to say how you actually use the mildots as a form of BDC at different ranges, example 1.5 Mildot at 300y.
        So yeah I'm well aware of the calculations to get range in both yards and metres;

        height of target (in inches)
        _______________________ x 25.4 = distance to target in metres or x 27.8 =distance to target in yards
        Mils

        Maybe this pic will help >


        All things being equal (same ammo etc), will a rifle zeroed at 100m have the same holdovers as the image above which is zeroed in yards?

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        • Guest's Avatar
          Guest commented
          Editing a comment
          Simple answer NO, the holds will be different.

        • Guest's Avatar
          Guest commented
          Editing a comment
          Short answer........No.
          And will get exponentially worse the further you go out.

          Edit:-
          Sorry, Didn't see Brent's reply.

          Mick.

      • #6
        Yep nice work fellas.
        I went through my old favourites list and found these 2 ballistic calculators I had saved a while back,

        JBM

        GSeven

        Both quite good but JBM I thought was best, ended up with this for my rig and the Federal 150g Soft Points it loves spitting out:

        Range Drop
        (m) (mil)
        100 -0.0
        200 -0.6
        250 -1.1
        300 -1.6
        350 -2.1
        400 -2.7
        450 -3.4
        500 -4.2
        550 -5.0
        600 -6.0

        You can of course do a much more detailed card, but this will fit nicely inside the rear scope cover.
        Cheers for the advice.

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