Calculate Distances With a Mil Dot Rifle Scope

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Mil Dot scopes are optics which allow users to easily calculate distances to a target without fancy equipment. Originally used by submarine periscopes, it has been scaled and re-implemented for military and recreational rifle marksmen to determine distance objects or to allow for bullet drop compensation. Once the basics are learned, calculating distances can be quick and painless using Mil Dots.

Steps

Background

  1. Binocular and periscope Mil Dots are not the same as rifle scope Mil Dots. They measure the same type of angular distance, but is actually 10 Mils instead of only one, which is more suited for marksmen use.
  2. A Mil is 1-6,175 of a circle. But to simplify calculations, the U.S. military calculates them as 1-6283 of a circle (previously 1-6400 on older scopes). Russian-based scopes are set to 1-6,000 of a circle. This means there is up to a 3% error in distance calculations.
  3. When looking at Mil Dots through a scope, one Mil is the distance from the center of one dot, to the center of the next dot (not the space between the dots). Each dot is .2mil and the space between the dots is .8mil for the round army type mil dot reticle.
  4. Mil distances on rear-plane cross hairs on a variable-power scope usually are only accurate at the highest power.

Measuring Distance

  1. Calculate the distance to the object by multiplying the height (or width) of the object by 1000 then dividing by the number of Mils that the object spans.
    • For example: a six foot tall object (2-yards) which is eight Mils in size is 250-yards away. 2 x 1000 / 8 = 250.
  2. Calculate as accurately as possible, and any "added error" (by yourself) is error in distance that may not be acceptable.
    • Sub-divide the Mil Dots as much as possible, and be as accurate in estimating the size of the object as possible.
    • The object is five feet (1.67-yards) wide and spans 2.8 Mils is 596-yards away.
    • A guess that the object is 2-yards instead of 1.67 would mean the estimation of over 100 yards difference which could mean a hit, or a miss of over five inches with a standard .308.
    • To be in the right mindset, calculate sizes of objects to the tenth of a yard (is that 3.4-yards or 3.5?). Calculate the span in Mils also to the tenth of a Mil. Both of these will take practice, but perfect estimations is the only way to get perfect range calculation.
  3. Use a calculator if needed. Some equations might get pretty complex, and accuracy is key, but the speed of a calculator may also help in some situations.

Tips

  • If you calculate using the size of objects in meters, the distance to the object will be in meters (for that matter, any measurement system will calculate accurately — size of target in inches to inches to target, kilometers to kilometers, fathoms to fathoms).
  • Stronger mounted scope also means you will lose sight of your target after the recoil. Less powerful scopes allow you to aim faster, and make quick follow up shots if needed.
  • Being able to keep the scope steady will affect how accurately you can measure the span in Mils of the target.
  • The Mil Dots can also be used for bullet drop compensation or windage adjustment.
  • For better distance calculations you will want to use high-end scopes on a tripod, because mounted scopes can be bulky, or get damaged if you drop the rifle.
  • Another formula you can use is (25.4 x inch of target)/mil reading = distance in meters

Warnings

  • Sloppy range estimate comes from sloppy estimation of size of the target and span of Mils.
  • Be sure to follow all state and local laws while shooting. Note that many laws on firearms change drastically from state to state, and can even change between counties or even cities.
  • Firearms can be very dangerous and even lethal. They should only be used by experienced firearm users or under the direct supervision of an expert firearm instructor.

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