2 Butcher Вы немного напутали. Действительно, в США есть mil :
a unit of distance equal to 0.001 inch: a "milli-inch," in other words. Mils are used, primarily in the U.S., to express small distances and tolerances in engineering work. One mil is exactly 25.4 microns, just as one inch is exactly 25.4 millimeters. This unit is also called the thou. With the increasing use of metric units in the U.S., many machinists now avoid the use of "mil" because that term is also a handy slang for the millimeter.
однако, это линейная единица измерения, и к вычислению расстояния в прицелах не применяется, в прицелах применяется угловая mil(она же тысячная):
a unit of angle measure, used in the military for artillery settings. During World War II the U. S. Army often used a mil equal to 1/1000 of a right angle, 0.1 grad, 0.09°, or 5.4 arcminutes (often written 5.4 moa; see "moa" below). More recently, various NATO armies have used a mil equal to 1/1600 right angle, or 0.05625° (3.375 moa). In target shooting, the mil is often understood to mean 0.001 radian or 1 milliradian, which is about 0.0573° or 3.43775 moa. In Britain, the term angular mil generally refers to the milliradian. 1 milliradian corresponds to a target size of 10 millimeters at a range of 10 meters, or 3.6 inches at 100 yards.
т.е. 100mils на американском прицеле - это ~те же 10м на дистанции в сто метров. С советскими есть небольшая разница - за счёт разного округления кол-ва тысячных в окружности -
# 1⁄6400 of a circle in NATO countries.
# 1⁄6000 of a circle in the former Soviet Union and Finland.
# 1⁄6300 of a circle in Sweden.