Technical question for all of you who know what you are doing

Discussion in 'Long Range Scopes and Other Optics' started by Lancet, May 28, 2012.

  1. Lancet

    Lancet Member

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    Hey guys I am having a slight issue with my rifle. I need to know what 1 mil-dot is equal to in MOA at 1000 yards. For example say 1 mil is equal to 4 MOA. I am asking this because I shoot low at 1000 according to my ballistic calculator, it gives me 24.5 MOA and I shoot appx. 2 feet low, but if I hold up 1 mil-dot in my scope it is almost perfect so I wanted to know what they are equal to so I can dial right in.

    Thanks
     
  2. coues7

    coues7 Well-Known Member

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    You better do some more reading on MOA vs Mils......
     

  3. JackinSD

    JackinSD Well-Known Member

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    1 mil at 1000 yards is 36 inches.

    If you are 36 inches (3 ft) low the MOA adjustment would be: 36/1.047/10= 3.44 MOA

    If you are just 24 inches (2 ft as you saids) the MOA adjustment would be 24/1.047/10 = 2.29 MOA

    Both answers rounded off.

    Like coues7 said, you may want to do a bit of reading on MOA and Mil.

    I am also asking myself, if you had more adjustment left in your elevation on your scope why you didn't walk it into the target. Since, you weren't sure how to figure it out.

    Anyway, best of luck.
     
  4. Bart B

    Bart B Well-Known Member

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    With three different units for click values on rifle scopes, and none of them are typically exact, one's better off to measure what their scope really moves the reticule per click as well as what gradient lines or dots are spaced at. Plus, all the same scopes of a given make and model will have slightly different amounts of movememt per click as well as the distance between gradient lines or dots have. That's 'cause all the lenses in a scope's optical system focusing the image on the reticule don't have exactly the same focal length. It's very normal for them to have a 4 to 5 percent spread.

    Don't shoot groups at different scope settings; that's not good enough. Instead, clamp your scope in something with it aimed at a ruler exactly 50 or 100 yards away from its front end, moving the adjustments put the reticule on an inch mark then move the adjustment enough to cause the reticule to move exactly 10 inches on the ruler. Divide 10 by the number of clicks it took to move the reticule 10 inches. If it's 36 clicks, each click's worth .2778 inch. If 42 clicks, each click's worth .2381 inch. Compare that with what the scope's specs say it should be.

    By the same method, measure how far apart the gradient marks or dots are. Do the same type of math. Then you'll know for sure.

    If you want to see how the reticule moves in angular MOA's, set the ruler at 95 yards 17.5 inches. One inch will equal one angular MOA at that range.

    Note that with some scopes, one MOA's meant to be 1 inch at 100 yards; the original and standard for the shooting sports. On others, it's meant to be 1.0472 inch, or what an angular MOA is and has been the spec on some makes and models. Some makes of scopes are not real clear as to which standard they use. Measure what your scope does then you'll know.
     
  5. BlackStreak

    BlackStreak Active Member

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    I would double check the inputs into the ballistic calculator. Re-shoot through a choronagraph numerous times on a couple different days or double check one chronagraph with another if you have access to two of them. Make sure your using the G7 BC and the correct G7 BC give for the particular bullet your shooting. Plus the atmospheric conditions such as InHg inputs affect point of impact in a huge manner. If all your inputs have been confirmed correct and your distance to the target is correct, then I'd start blaming the scope.
    For shooting distances approaching 1000 yards and more, a scope level that's true to the verticle reticule is a must because any cant will cause a lower POI.
    I validate my scope adjustments not through a ruler but by shooting 5 shots at 100 yards. Then adjust up 10 MOA and shoot 5 more shoes at the same point of original aim. Then agjust up 10 more MOA. Again use the original aim point. This will show you two things. Your groups should be in straight up from one another, if not your level isn't true with the scope. Then measure the distance between the center of the groups. Then divide the distance between each group by your 40 clicks used to adjust up 10 MOA. Sometimes the value of one click in the first 10 MOA is has more or less value than the clicks in the second 10 MOA.
     
  6. Scot E

    Scot E Well-Known Member

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    Great Info above! Do this and you will be way ahead of most shooters!

    Also keep in mind it may be other issues as well, like BC or velocity error that is causing some or all of the issue. But like Bart said, get the scope calculations figured out exactly first then you can start looking at other issues if needed.

    Scot E.
     
  7. Bart B

    Bart B Well-Known Member

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    I made a boo-boo in these instructions:
    If the ruler's at 50 yards, move the reticule such that it moves only 5 inches. That's going to change the adjustment the same number of clicks as 100 yards.....at 50 yards, one MOA's only half as much on the ruler as it is at 100 yards.

    One other thing, with the scope focused at 50 yards, you'll get a couple more clicks moving the reticule 5 inches as the scope's objective lens is further forward making the target image a tiny bit bigger on the reticule. So it's best to use 100 yards to be more precise. . . .if you have enough space to do it.
     
  8. Bart B

    Bart B Well-Known Member

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    One other thing I've found interesting about rifle scopes is how much movement's available in all four directions when the elevation and windage knobs are set such that the reticule's dead centered on the scope's mechanical axis. After doing this, then bore sighting to see how far off the mounting rings and bases are aligned with the bore axis. Some rifles with some sets of bases and rings are pretty bad.

    First, make two V blocks then attach (nail, screw) them to a board several inches apart such that the scope can rest in them and spin free. Then clamp that board in something that you can see stuff through the V's at least 25 yards away.

    Second, take the scope out of its rings, lay it in the V blocks, look through it then rotate it. The image will spin in a circle of some amount.

    Third, move the adjustments as the scope's spun in the V blocks until the image rotates about a single point. When this happens, the scope's internal tube that's moved by the adjustments is now centered and well aligned with the main tube axis.

    Put the scope back in its rings on the bases then check its alignment by bore sighting. See where the bore points relative to where the scope's reticule is. Prepare to be surprised.
     
  9. Scot E

    Scot E Well-Known Member

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    Very true. This is one of the reasons I like the Burris Signature Rings so well. You can eliminate all of that error with the rings and have all of the internals for dialing and shooting.

    Scot E.