First of all, what are we talking about? Have you ever seen the following image before?
The dots on the cross-hairs is what we’re talking about. They are a pre-measured distance apart inside the scope. Since we view the dots through the scope and our eyes overlay them onto the image we see through the scope, they end up being helpful for determining distances in our vision. This is usually for the purpose of “walking” shots onto an intended target or adjusting for bullet drop at distance. This is immensely aided by having “matching turrets”, which we will touch upon later.
And you though that you’d never need trigonometry in real life, huh?
The shooter is at the left point of the triangle
‘d‘ is the distance between the shooter and the target
‘h‘ is the calculated height or width of the target
‘Θ‘ is the angle measured in the scope, in either MoA or mils
MoA: Minute of Angle. One sixtieth of a degree. A circle is divided up into 360 degrees, each of them can be further divided into 60ths, which are minutes of angle.
Mils: Milliradians. A full circle can be divided into 6.283185307 radians (pi x 2). Each radian can be divided into thousandths, a ‘milli’-radian, like a thousandth of a meter is a millimeter.
MoA vs. Mils
In my mind, it comes down to this: I use the standard system, sometimes called the ‘Imperial’ system. I live my life in feet, miles, pounds, inches, gallons, ounces, etc. I leave the metric system and it’s fake-usefulness to Europeans and idiot Americans who think that being able to swap units by switching decimal places is somehow advantageous.
The standard system uses degrees to measure angle, radians are the domain of the metric system. I’m an standard system guy and have no use for the metric system. I have the same lack of use for scopes graduated in mils. If you live your life by the meter, liter, and kg, go mil. You’d be dumb not to.
This is really where the differences start to show. Warning: Math Ahead!
Note: I will use the term ‘height’ in the following paragraphs. This is interchangeable with ‘width’ as far as distance calculations are concerned.
Note: To calculate the distance to the target, you have to know the object size. To determine object size, you have to know the distance to the target. You have to know either the distance to the target or the size of the target. If you know neither, you need to make some guesses and prepare to miss. This is also why laser range finders are so popular.
By a huge coincidence (as far as I can tell) in the math, 1 MoA = 1.047 inches at 100 yards. Most MoA shooters simplify it to 1 inch at 100 yards, which yields a sub-5% error. That is a level that just about everyone can live with, as almost every other variable involved will have an error higher than 5%.
Determining distance to target: Target’s height in inches, times a hundred, divided by the target’s height in MoA, equals the distance to the target in yards. For example, take the 12″ x 12″ plate…
The 12″ x 12″ plate stretches 1.5 minutes (a dot and a half) both above and below the cross hair, meaning it’s 3 MoA tall.
(12″ x 100)/3MoA = (12*100)/3 = 400 yards.
Determining object size: Object’s height in MoA, times the distance to the target, divided by 100, yields the size of the object. We’ll use the same image as before, but let’s put it at 523 yards…
The plate is 3 MoA in height, and sits at 523 yards.
(3 MoA x 523 yards)/100 = (3*523)/100 = 15.7 inches tall.
Determining distance to target: Target’s height in cm, times 10, divided by mils, yields distance to object. If you have the target’s measurements in mm, forgo the ‘times 10’. Take this 12″ x 12″ plate. Don’t forget to convert from inches into cm or mm, and then meters back into yards…
((12″ x 2.54 cm to inch) x10 * 1.094 yards to meters) / (1.5 mils)
= (12*2.54*10*1.094)/1.5) = 222 yards.
Determining object size: Object’s height in mils, times the distance to the target, converted into meters, divided by 10, yields the size of the object in cm, which needs to be converted into inches. We’ll use the same image as before, but let’s put it at 352 yards…
(1.5 mils * 352 yards * 2.54 cm per inch )/(1.094 yards per meter * 10)
=(1.5*352*2.54)/(1.094*10) = 19.0 inches.
So, What Should You Get?
MoA and mils are both just as capable, but each needs units in it’s own system in order to work. There’s no reason to choose a scope that requires units you don’t normally use. The key here is that if your brain works in standard units, converting into metric and converting back out again makes you do more math than is necessary. More steps mean more chances to mess up, and you miss a shot. Maybe it’s on a steel target. Maybe you miss a monster buck on a multi-thousand dollar hunt. Maybe you hit a hostage instead of a hostage taker.
The only time that you should consider getting the wrong system’s scope is if you are part of a team that is already running the wrong stuff and you need to be able to communicate with them. If you’re part of a US-based shooting team, your teammates are probably running mils. Why? Because of institutional inertia.
The first guy to buy a good scope decades ago bought a scope with mils because there probably wasn’t any quality MoA scopes and he learned to run it well. He convinced other people to buy mil scopes because he was using it effectively. Now you’ve got a team of guys using mil scopes to an acceptable degree. If you show up with your MoA scope because you’re not Eurotrash and you use feet and yards and inches, you’ll be the one who can’t communicate info back and forth with your teammates. As much as I hate to say it, the need to communicate trumps buying the correct gear.
This means the dots in your scope and the adjustments on your scope match. If you have your dots in mils and your turret clicks in MoA, then you’re literally trying to move in one system with another. You’re trying to measure a 5 foot width with a ruler in meters, or determine the amount of pounds an object weighs with a scale that only reads Newtons. Scopes with MoA turrets and mil reticles were an abomination that arose from a misunderstanding. The fact that anyone managed to hit anything with them at all is a testament to the skill and determination of the shooter, even when saddled with bad equipment. If you pay money for a scope that doesn’t have matched turrets in today’s world, you are a fool. Anyone who promotes buying mismatched scopes is actively making the world dumber.
“I award you no points, and may God have mercy on your soul.”
If your car’s speedometer reads in mph, use MoA. If your car reads kph, use mil. If your football can be carried and thrown, use MoA. If you use the metric system in your normal life, go mil.