From: Louis Boyd <boyd@apt2.sao.arizona.edu>
Subject: Re: Sniper Rifles Rule!!!!!!
Date: 27 Jan 1998
Newsgroups: misc.survivalism

david hughes wrote:
>
> Eric Williams <wd6cmu@netcom.com> wrote in article
> <wd6cmuEn909B.Gx@netcom.com>...
> > I'd like to hear some techniques for using mildots.  The formula I
> > came up with after doing some trigonometry was:
> >
> > (Size of object in inches x 28) / (size of object in mils) = range in
> > yards
> > 
> > But I've seen elsewhere that the conversion factor is 25.4 rather than
> > 28. Which is right?
> > 
> > I usually use 70 inches for a standing man, 50 for kneeling, is this
> > right?
> >
> > Any shortcuts to just doing the math?  I figure you can compare 1/4 mil
> > dot size to head size for rough estimation at some ranges, but don't know
> > how effective that is in practice.
> > --
> >   Ask not what your country can make other people do for you.
>
> The simplest way is  (size of object in millimeters) / (size of object in
> mils) =range in meters.  Just teach yourself to use the metric system.
> Average man = 175 mm
> Beer can = 130 mm
> Kneeling man = 120-125 mm
> Human head = 150 mm

The beauty of the mil dot system is that it doesn't matter what units
you use, as long as you are consistant.  The if the spacing of 1 mil
through the scope is X units high, then it is 1000 X units distant.
The units can be feet, yards, or meters, it doesn't matter.  If you
want the answer in yards, think of how many yards one mil subtends.
Example: If one dot spacing is .5 yards (18") high, then the distance
is 1000 * .5 = 500 yards away.  A 6' tall person would subtend 4 dots
at 500 yards, or 2 dots at 1000 yards.   If you want the answer in
meters Mr Hughs' advice is fine.  The metric system has advantages at
times.

The problem with the mil dot system (as compared to a laser
rangefinder) is in estimating the actual size of the target.  Sometimes
it's easy, sometimes not.  Mil dot accuracy in terms of percent range
accuracy will be the same as the error in esitimating the target size.
If you think a man is 6' tall and he's 2 mil high in the scope, but he's
really 5'6" you will think he's at 1000 yards when in fact he's at 917 yards.
If your're shooting a .308 you will shoot high by about 80 inches. Not
even close, and that isn't considering any other error sources.
At ranges 400-700 yards the mil dot system works pretty well.
Closer than that you probably don't need anything other than an eyeball
estimate (with a little practice).


Lou Boyd
FCSA NRA