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Who wants some Pi with their milrads?

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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/20/2013 at 12:38
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Optics GrassHopper
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Hi!  I'm new to the forum and wanted to start off with a very specific question.  First a little background.  I've been around firearms forever, but have always longed for something a little more "long range."  As a lefty, I decided to go with the Savage FLCP-K in 308.  For glass I'm thinking about either the Weaver or Vortex Viper in mils/mils.

Now for the question.  I'm enjoying learning all about the different measurements, adjustments, etc, and it is pretty much just a trigonometry game (a very very complicated one at that). So when I'm looking at scopes listed as mils, are they truly milli-radians or something else?  I've seen 1/6283 (a true thousandth of a radian), 1/6400, and even a few others.  According to my calculation, this comes out to either 0.0573 or 0.0563 degrees for 1 milrad.  At 1000 yards, that is about 0.66 inches as far as I can figure.

I am not planning on shooting that far anytime soon.  And I know with all the factors to consider, half an inch at 1000 yards might not even be recognizable.  My problem is I'm an engineer, and I like to know how things are really designed, manufactured, etc.  So are milrad scopes truly using 2*Pi radians for a circle, or a value of 6.4, or does it depend on the manufacturer?

Thank you!

Jesse
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/20/2013 at 12:46
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1 mil = 1 meter at 1000 meters, or 1 mil = 1 yard at 1000 yards

scopes in mils are usually 1/10th mil. generally the finest adjustment in scopes is 1/8 moa per click


Edited by stork23raz - March/20/2013 at 12:53
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/20/2013 at 14:25
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Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/20/2013 at 14:44
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Optics GrassHopper
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According to the PDF, milliradians are truly based off 1/(1000*2*Pi).

I've read some things that assume 1/6400 for calculations, so I was wondering if some scopes use that value for some reason.  Or maybe they are just trying to make the math a bit easier for people, tell them to use 1/6400, even though the equipment is really built to 1/6283.
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: March/20/2013 at 15:23
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I don't think you'll find any modern scopes based off anything but true milliradians...except maybe the ripoff CounterSniper brand makes some other variation a $1000 "feature".
 
The thing you'll find is that, first, it's hard to range with a reticle. And the farther out, the more critical the measurements and calculations become. So it is best to use accurate numbers. I've found it easiest to think in these terms:
 
  1. Convert the target's size to a decimal, regardless of units (yards, meters), e.g. 18" = .5 (yards)
  2. Multiply that decimal value by 1000, e.g. 500 (yards). The target would subtend (span) 1 mil at that distance
  3. Divide the distance by the actual number of subtensions, e.g. 500/.7 mils = 714 yards or 500/2 mils = 250 yards
Post Options Post Options   Thanks (0) Thanks(0)     Back to Top Direct Link To This Post Posted: April/11/2013 at 13:00
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In my research i have found one main thing about the milliradian concept as applied to scopes. It is one of the most bastardized and complicated systems ever developed. Just look at the size and configuration of the dots themselves-- round dots set up to subtend .2 mil, and some at .22 mil. used to interpolate .1 of the mil. unit. Oblong USMC dots were designed to subtend .25 mil. set up to interpolate to a quite complicated .125 of the mil. unit. Some mils were set up to use an angle of 1/6283 of a circle, and then some were changed to 1/6400th.

Understanding the mil applications/history would be a college course unto itself.

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