When deciding what scope to buy, one major decision is which reticle selection is best for you - MD (Mil Dot) or IRF (illuminated Range Finding). Please read below to learn the difference between the two reticles.

 

MIL DOT OVERVIEW

A Mil-Dot reticle is named for the dots and spaces it is composed of. The space between the dots is one milliradian, or “mil” for short. A mil is a unit of angular measurement, like degrees or minutes of angle. It represents one unit of angular width for every 1,000 units of distance. This arrangement is very useful for determining the distance of objects of a known size.

If the size of an object is known, its distance can be calculated as follows. Measure the object with the reticle, counting how many mil sections it covers. Dividing the size of the object by the number of mils and multiplying by 1000 can now calculate the object’s distance.

(object size/quantity of mils) x 1000 = distance

Note that the unit of measurement used for object size and the calculated distance will be the same. That is, if the object size is in yards, the calculated distance will also be in yards; if size is in meters, distance will be in meters. Example: An object has a height of 2 yards. With the reticle, this object is measured and found that it covers exactly 5 mills. (2/5) x 1000 = 400 yards

Or if the same object is measured in meters: (1.83/5) x 1000 = 366 meters

TRAJECTORY & DEFLECTION

To accurately engage a target at a distance greater than sight-in, requires that the trajectory of the specific load being used is well understood. This is available from ammunition suppliers, derived from external ballistic software, or determined by actual use. In the above example, an object’s distance was determined to be 400 yards. If zeroed at 100 yards, a specific load may drop by 25.6 inches at that distance. The value of one mill at 100 yards is slightly greater than 3.6 inches. (This equates to 7.2 inches at 200 yards, 14.4 inches at 400 yards, and so on.) Knowing this, it can be calculated that a little less than 2 mills of up elevation is needed. The reticle can then be used as a “hold over” guide to quickly engage the 400 yard target. If susceptibility to wind drift is known for the load being used, the dots on the horizontal axis can be used in a similar fashion as references to compensate for wind deflection or lead in the case of a moving target.

Ideally, adjustments for distance and deflection should be made with the windage and elevation knobs. But the mil-dot reticle is a useful quick aiming reference.