MIL vs. MOA
Welcome to the Thunder Dome!!!
Alright here we go, I’m hesitant to even bother traveling this path because of it’s likeness to other legendary topics of controversy like .45ACP vs. 9x19mm or AR15s vs. AK47s that have become the bane of internet forums. With remarkable predictability the discussion always seems to spiral into feverish mad debates only matched by the topics of politics and religion. However, if you’re seriously interested in long range shooting then this is something you’re going to have to navigate sooner or later. So put on your boots because we are about to step knee deep in the topic of MIL vs. MOA, what they are, why we use them, and which is best for you.
A Rose By Any Other Name…
Brace yourselves…a MIL and MOA are practically the same thing. MIL, or more correctly Milliradian and a MOA (Minute of Angle) are both angular units of measurement. I know I just made some heads explode, so take a moment to go scrap the gray matter up and let’s explore why they are essentially the same.
Most of us remember from our high school geometry class using degrees to express or measure an angle.
Now lets imagine using a different unit of measurement to express angles, just like we might use inches instead of a foot or even centimeters to express the length of an object.
Breaking It Down
Angles are the measurement of a plane angle which is created when you have two straight lines diverging to or from a particular point. Whether you decide to use degrees, Minutes of Angle or Milliradian to express your measurement, you are still measuring the same thing.
As it turns out sometimes just like our carpenter, we need to measure things in smaller chunks. Most of us are familiar with breaking up 1 foot into 12 inches in order to have a more useful measurement, so now we can take 1 Degree and break it into 60 smaller pieces of pie called Minutes of Angle.
Conversely the Milliradian might need a bit more explaining. While the jump from Degrees to Minutes of Angle is easy for most Americans, the European born Radian and its subtention, the Milliradian, might require another cup of coffee.
A Radian is the arc of a circle with the same length as the radius of that circle.
As we can see that is a kind of clever metric for measuring out angles and if you’re a real math nerd it gets better. If you take half of a circle (180 Degree) and squeeze as many Radian in there as you can, you end up with…wait for it…3.1415 or 1π Radian, which is Pi for you non-nerds. Naturally the circumference of a complete circle comes out to 2π radians.
Now for the Milliradian, as the latin prefix Milli suggest, a Milliradian is in fact a 1/1000 subtension of 1 Radian. And if you do the math you’ll find it takes 6283 Milliradians to make a complete circle.
So why the hell would anybody use Radians? The short answer is from a mathematical point of view it wonderfully stiches things together. More importantly Radians have long been the standard unit to address angles across advanced fields of mathematics since the 1800s. I suppose the next question to address is how do these systems of angular units come into play for long range shooters?
Both the MIL and the MOA can trace their ballistic lineage back to the rise of field artillery during the first world war. The Brits championed the use of Degrees and Minutes which they’d been using for awhile, while the French played with the Milliradians and would developed a 6400 MIL per circle system as opposed to the mathematically correct 6283 per circle. In a nut shell it turns out that 6400 makes it a bit easier to do math on the fly and its close enough for government work. Naturally the use of the use of MILs and MOAs trickled down from the artillery observations and adjustments, to machineguns travers and elevation mechanisms and then finally as technology progressed into sniper rifles optics we began to see a divergence between the use of the two.
Early on Milliradians became extremely popular for artillery and machineguns after the NATO standardization of the 6400 system in the 1950s. Unfortunately, the Milliradian didn’t lend its self to the precise sight adjustments need for delivering accurate rifle fire. A 1 MIL adjustment would move a sight a linear distance (up/down, left/right) 1 meter on a target placed 1000 meters way. Obviously this is system is fast and intuitive for area weapons, as the error is nearly irrelevant in considering the effectiveness of bursting artillery or machinegun beating zones. But even close in at 100 meters a MIL adjustment has a rather large linear movement of 10 centimeters which isn’t terribly indicative of good precision rifle work.
This seeming lack of practicality meant that the MOA would remain the prominent sight adjustment for precision rifle fire. The MOA subtends to a much smaller and useful linear measurement, at 1.047 inches across at 100 yards it nearly seems to be a match made for the American shooter. As precision rifles advanced in capability they required more exact adjustment in their points of aim, industry accommodated us by breaking up the MOA into more refined fractions.
But not all was well in Paradise, especial for the military sniper. While I might wax poetically about the natural history of the sniper, what’s important to grasp is he stood at the cross road of MILs and MOA for well over 50 years. On one hand he called artillery, directed machineguns and gauges distances and headings with one angular unit of measure and sighted his rifle with another.
Needless to say after half a century of having to convert measurements between MILs and MOA, we snipers finally decided we had better ways to spend our time on the battle fields. The solution was painfully obvious and something the Europeans had already done it. Take the Milliradian and subtend it into 0.1 in order to make it useful for precision rifle applications. What you end up with is a practical adjustment for sights that provide a linear movement of 1 cm at the distance of 100 meters.
What’s right for you?
The big question from a lot of new shooters is always “which system should I use?”
Given the fact that they are both equally well founded systems of measurement, the choice comes down to a personal preference. Although consider heavily your shooting discipline and what system your peers are using. Sometime people forget the communications aspect of most long range shooting disciplines and nothing is more flustering dumping rounds at a $1 a pop (…or sometimes more) because you and your shooting partner are on two different sheets of music.
Gimme Them MILs
That said case for using MILs is strongest among Military (and Law Enforcement), as most professional snipers have switched to this system due to it’s time saving practicality when considering unknown distances and the integration of other military applications. This professional embracement has lead to prolific use among long range marksmanship instructors many of whom are products of the various military intuitions. Naturally any armature seeking to progress his or her skills beyond a mere recreational slinging of lead might seriously consider adopting. The MIL is also extremely convenient for those of us who prefer decimals to fractions. I for one can’t stand using fractions and decimal base systems are a God send.
MOA All Day
As MOAs go, they still have a strong following in the completive world, disciplines like F-Class, Palma and Service Rifle all have rich histories with the MOA. Practically speaking many of these disciplines require optics subtended down to 1/4th or 1/8th MOA in order to be competitive and the 0.1 Milliradians adjustments are often simply not refined enough for these styles of shooting. American hunters will still also tend to gravitate towards the MOA for its simplicity just as much now as they did 50 years ago. Contrary to the MIL if you are somebody who prefers to work in fractions like many of us who grew up using imperial units are, then the MOA might be more intuitive to pick up.
In closing the choice between MILs and MOAs comes down to what is going to work for you. Having the basic knowledge of angular units that we just covered should help you work that choice out. Just remember that when we use MILs and MOAs we are literally communicating the same thing…angles, just in different languages.