Mil Dot calculation formula
The mil dot system was first developed in the 1970s by the U.S. military. The military uses the system for artillery, mortars and sniper rifles. The mil dot system is also found on commercial rifle scopes.
A mil dot rifle scope uses a mathematical measure called a milliradian. The center of each dot, or box or line, depending on the scope manufacturer, is 1 milliradian away from the next dot's center. The length of a milliradian derives from an angular measurement of a circle, which is a complex calculation but fits into a simple formula for estimating distance. There are 6, 283 milliradians in a circle, but this measure was rounded up by the American military to 6, 400 milliradians and rounded down by the previous Soviet Union to 6, 000 milliradians.
The basis of the mil dot system is that the dots or lines on the scope can be used to estimate how far away an object of a known size is from the scope. For example, a sniper can identify a man in the distance as being about 6 feet (1.8 meters) tall, and use his height, along with interpretation of the dots on the scope, to figure out how far away he is. There are a variety of methods hunters or snipers can use to calculate range using a mil dot rifle scope. The scope crosshairs, or the dots, are lined up on the target. The rifle must be held steady for accurate ranging.
The most widely used method is to center the crosshairs of the scope on the target. Centering the crosshairs on the base of the target allows for easy calculations, because the dots can be read up along the vertical line. Then the dots are counted so the shooter knows how many milliradians tall the target is. It is essential that the shooter knows in advance how tall the target is in either imperial or metric measurements. For example, a hunter will generally know approximately how tall a rabbit or deer is.
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