Binoculars with Mil Dot reticle
The last post about scope reticles brought a lot of questions about the mil-dot reticle. I'd like to explain what a mil-dot reticle is and how it helps airgunners.
A mil is an angular measurement. There are 6, 400 mils in a circle, so one mil covers approximately 3.6" at 100 yards or close to 36" at 1, 000 yards. Military forces around the world have used the mil for decades for range estimating - most often to adjust indirect fire (artillery and mortar). Most military binoculars have a mil-scale reticle etched on the lens on one side.
A mil-dot reticle is a special type of mil reticle etched on the lens of a telescopic sight. Eight dots is sort of standard, but there are reticles with more than eight dots.
In scopes of fixed power, the reticle is used just as it appears. In variable scopes, there is just one power setting at which the mil dots are seen at the correct separation relative to the target. In most variable scopes, this is the 12x setting. The dots are separated from each other by one mil, so the distance from the center of one dot to the center of the next dot is one mil when the scope is at the correct magnification.
This mil-dot reticle has 12 dots on each line, instead of the more common eight. From the center of one dot to the next is one mil, when the scope is set to 12x.
Mils for range estimation
Mil reticles are used for range estimation by the military, where the size of equipment is more or less standard throughout all the armies of the world. The length and width of main battle tanks are very similar everywhere. A soldier can measure the number of mils between the sides of the tank and use that number to calculate the approximate distance to the target. For example, a main battle tank is about 12 feet wide. At 1000 yards, one mil is very close to one yard. If a tank measures three mils across the front, it's about 1, 000 yards away.
For adjusting indirect fire it's even easier. The forward observer simply measures the amount of correction between the target and the last explosion. The fire direction center knows where both the forward observer and the target are, so the mil angle reported can be correctly transcribed from the forward observer's viewpoint and interpolated for the corrections to the guns. But that is of little interest to an airgun hunter.
TIANZHE Mauser 6×24 Tactical Binoculars with Mil-dot Reticle Black