MIL-Metric...Centimeters/Meters
100% WRONG. A radian is neither metric nor standard measurement.
It doesn't matter the measurement system as a radian is a trigonometric description.
A radian is an arc on the outer circumference of a circle that is equal in length to the radius. The angle subtended from the center of the circle to the outer ends of the radian arc is the radian angle - 57.3 degrees per radian.
There are 2Pi radians in a circle or - 6.2832 radians.
Why 2Pi radians? Because the circumference of a circle is: C = 2 x Pi x R (radius).
Isn't that interesting...? The circumference is 2Pi radiuses and there are 2Pi radians in a circle - Holy moly - it's the same thing - just a different way to describe it!
Just like a radius is neither metric nor standard - neither is a radian. Either distance (radius or radian arc) measurement can be in inches, centimeters, furlongs, nautical miles, chains, rods or any other type of length measurement.
A milli-radian is simply 1/1000 of a radian as "mil" is one thousandth. So, there are 6,283 milli-radians in a circle, each one having a milli-radian angle of 0.0573 degrees (1/1000 of 57.3).
MOA -English Standard Inches/Yards.
100% WRONG AGAIN. Minute-of-angle (MOA) is simply a different description of an angle subtended at the center of the circle.
There are 60 minutes in 1 degree. There are 360 degrees in a circle. 60 x 360 = 21,600 minutes in a circle. Minutes are not metric or standard - they're just a description of an angular unit.
As with a MIL, you can see that there is not a unit of measurement associated with the MOA description. It is a geometric description instead of a trigonometric description.
1 MIL angle = 3.438 MOA
At 100 yards - 1 MIL = 3.6 inches.
At 100 yards - 1 MOA - 1.047 inches
At 100 yards - 1 MIL= 91.44 millimeters or 9.14 centimeters
At 100 yards - 1 MOA = 26.59 millimeters or 2.66 (rounded up) centimeters
Instead of yards, we could change the distance to meters and still have inches or millimeters / centimeters for the MIL or MOA measurement at the end of the 100 meters. It doesn't matter because MIL and MOA are simply describing an angle that can be extended to any distance in any measurement system.
As you can see - neither MIL nor MOA have any relationship to a specific unit or type of measurement - they are simply different descriptions of angular measurement.
I understand - it's math and that's even harder than English...