Most American shooters are grounded in the older imperial units of the inch, foot and yard. The metric system was presented as an aside, not really emphasized and little used. But engineers and scientific types are wed to the metric system. Nowadays speedometer dials are in miles per hour and kilometers per hour while our food container labels are in ounces and liters or ounces and gram for weight. Eventually the metric system will be fully incorporated in the American way of life.
Metallic Silhouette Shooting
Until that happens most shooting sports use feet per second for velocity, distance in yards and bullet weight in grains with 7000 grains to the pound. One area where metrics are used are in metallic silhouette shooting, it being an import from Mexico and all. Except for a few caliber designations we are free from metrics.
Minute of Angle (MOA) Calculator
Mils and MOA are systems used by shooters and the military to measure angles, and the MOA is a measurement of inherent accuracy. MOA is minute of angle. An angle, like the hour is divided into minutes and seconds. One MOA is angle width at one hundred yards of about one inch (1.047 inches). So, at 200 yards the width is 2 inches and 300 yards at 3 inches and so one, 1 inch per every one hundred yards. At a thousand yards a 1 MOA group would measure about 10 inches in diameter. MOA is a measure of accuracy and precision. Incidentally good target rifles can shoot to sub MOA groups and even sub half MOA or 30 second groups.
The US military and NATO use 6400 mils to a full 360-degree circle. But the term mil, is short for a milliradian. A radian is the angle subtended that is equal to the radius. This is the calculus unit used to calculate angles. It is equal to 180/π or rounds off to about 5.30 degrees. There are 2π radian in a circle or 6.28 radian to 360 degrees. A milliradian is 1/1000 of a radian leaving us with 6283.18 milliradians in a circle. An inconvenient number to do math with. So, by agreement 6400 radian was used, about a 2%, actually it is only 1.82%, acceptable for most practicable purposes.
Milliradian Distance Calculator
The mil is used to sight artillery and for navigation. Most military compasses have an inner ring below the degree ring marked in mils. But mils are handy, they can be used to determine range by a shooter and are used by snipers. Mils have a unique property, on mile equals 1 unit at a 1000 unit. One-foot arc at 1000 feet, 1-yard arc at 1000 yards, etcetera. Many a precision rifle scope are marked in miles and are accurate at one magnification. Take a human in summer clothing he is about 22 inches wide on average. The scope is marked in 1 mil dots. If a man is about between two dots wide how far is he?
Range = 1000 x target width/mils
Range = 1000 x 22 = 22,000 (inches)/2 = 11,000 inches or 11,000 / 36 = 305.6 yards.
A mule deer averages between 31 – 42 inches at the shoulders, nose-to-tail length of 3.9 to 6.9 feet. A fully mature mule deer buck will have eight points including the brow tines.
Let’s say it looks like a mature eight point buck, and we will use an average height of 36 inches at the shoulder.
Range = 1000 x 1/3.5 mils, the converted the inches to yards so our answer will be in yards.
Range = 1000/3.5 = 285.7 yards.
Mils and MOA’s are handy. There is about 3.6 inches to a mile at 100 yards. Some principles to think about.