Like any technical issue, rifle scopes have a language all their own. This language is often a jumble of acronyms, insider jargon, and technical terms with obscure meanings. The two most popular measurements used in rifle scopes add to the confusion. What are MIL and MOA, and how do you read the numbers on the scopes?
MIL and MOA are both units of measurements used in estimating distances in rifle scopes. Both measurements reflect angles visible through the scope. MILs or milliradians measure use an angle of 57.3 degrees for these measurements. MOA stands for Minute of Angle. A circle has 21,600 minutes which provides a basis for making estimations of distance.
In the US, the most popular method of measuring rifle scopes is MOA. Most rifle scope manufacturers sell scopes for either measurement type. However, MOA dominates shooting sports. It is important to be familiar with both types of measurements and how they work with your scope adjustments on the range.
Moment of Angle (MOA)
Let’s take a circle. There are 360 degrees in a circle. If we subdivide each of those degrees into 60 minutes, we find that a circle has 21,600 minutes. (Quit thinking about the clock. We are talking measurements of angles, not time.)
IF your rifle scope has marks divided into one MOA units when you look at a target 100 yards downrange, you can easily estimate the target’s size using the hash marks. At 100 yards, each has mark on an MOA reticle equals about 1.04 inches.
Knowing that the hash marks on your reticle equal about 1.04 inches at 100 yards, you can do some amazing estimations. If you know the range of your target, you can estimate the size of your target. If you know your target’s size, you can calculate reasonably well the distance to your target. With the range to your target known, calculating hold over or windage is simple, and the adjustments to your scope are quick to make.
Contrary to popular belief, MILS does not have anything to do with military terminology or usage when used with scope measurements. The MILS stands for milliradians. Another popular acronym used for this angular measurement is MRADS.
Let’s look at our circle again. This time we divide the circle into 1000 equal slices. Each of these slices is one milliradian. One MIL or MRAD at 100 yards is equal to 10 centimeters or approximately 3.6 inches. Even at 100 yards, 3.6 inches is too large for fine adjustments. Scopes that use MILS typically divide the measurements into tenths.
For example, at 1000 yards, a scope with adjustments based on a tenth of a mill will move the reticle .36 inches with each click. If you are comfortable using metrics, that equates to 1 centimeter at 100 meters. The beauty of MILS is that it is independent of the measurement scale. One MIL at 1000 yards equals one yard. At 1,000 meters, a MIL scale scope equates to 1 meter. Whichever measurement system you use is workable with a MIL scope.
Reading an MOA Reticle
Standard MOA reticles show a hash or tick mark on the crosshairs for each MOA. These tick marks appear on both the horizontal and vertical crosshairs. Using the tick mars on the reticle, a shooter can estimate the amount of holdover adjustments or windage adjustments needed. These adjustments are made to the scope using the turrets.
Reticle Differences in MOA Scopes
Each scope manufacturer has a proprietary version of an MOA scope reticle. These proprietary versions of MOA reticles can help a shooter perform several functions, such as:
- Range estimation
- Holdover adjustment estimation
- Windage adjustment estimation
- Bullet drop compensation estimation
All these estimations and corrections are doable using just a simple MOA reticle. However, the additional information provided by these proprietary scopes makes the process faster and easier for most shooters.
MIL or MRAD Scope Reticles
To the untrained eye, a MIL reticle and an MOA reticle look almost the same. The differences are not that much. MIL dot scope reticles have hash marks or dots on the crosshairs representing one MIL at 100 yards. You must remember that 1 MIL at 100 yards equals 3.6 inches. One MOA at one hundred yards equals 1.04 inches. That is a large difference in the world of long-range shooting.
MIL dot scopes are used more for range estimation than anything else. While Mil dots can be used for windage and elevation estimation, most shooters who use a MIL dot scope rely on other tools for windage and elevation adjustment calculations.
Which is Best – MOA or MILs?
Both types of scope reticles perform well in the hands of someone who understands the basics. MOA measurements are the most popular in the US, but that doesn’t hold elsewhere. In many countries where shooting sports are popular, MIL dot reticles find favor. I think this is due to the differences in measurement types from country to country. Shooters in the US are not as familiar with the metric system as are shooters in Europe and other regions.
In truth, the best is what you can use effectively. Training and practice can make a difference. Once you learn the basic methods, wither style of scope measurement will work. Both types of scope reticles are accurate and reliable in the right hands.
Using a MIL dot or MOA Reticle to Zero Your Scope
I don’t know how many times I have watched an inexperienced shooter trying to zero a scope at the range with little success. It is apparent that these shooters have no understanding of MOA or MILs and make haphazard and random adjustments to their scope’s turrets. They chase the shots over the target without any plan. Zeroing a scope can be easy if you follow a few basic steps.
Step 1 – Set Yourself and the Target Up Properly
Start with the proper target. I prefer the Optic Zero targets from ARMA dynamics. You can get these targets at most ranges or shooting stores. I like these targets because each target has five aiming points and the grids on the targets match the measurement style of your scope.
Place the target on a secure stand 100 yards from the shooting station. Speaking of your shooting station, support your rifle properly so that you make repeatable shots. I prefer sandbags to a bipod, and I like to support my rifle on the foregrip and the buttstock not to hold the rifle’s weight when I shoot. Consistency is the key to a good zero on your rifle scope.
Another handy tool is a good spotting scope. At 100 yards, most of us can’t see the last bullet impact. If your rifle is shooting up to expectation, you will need some kind of spotting scope to differentiate your hits on the target. Make good notes, diagram your shot patterns, and don’t leave anything to chance.
Step 2 – Take your First Shot Grouping
I prefer to shoot three-shot groups when I am zeroing a new rifle and scope combination. Even the slightest difference in loads, wind, and technique, can cause changes in the point of impact. A three-shot group gives you a good indication of the consistency of your loads and your file.
I always try to start with the aiming point on the upper-left side of the target. I work in a clockwise pattern and save the center bullseye for my last grouping. Set the crosshairs of your scope on the center of the aiming point and take three careful shots. Diagram your pattern in your notebook.
Step 3 – Estimate the Corrections
Examining where your shot’s impact will tell you almost immediately how much correction to make to your scope. For example, if your shots are low and the left of your aiming point, count the number of grid squares from the aiming point.
Estimate where the center of the three-shot group lies on the target and use that point for your corrections. The relative center of the shot group represents the average point of impact of the three shots.
If your shots are 2 inches low and 1 inch to the left, if you are working with an MOA scope at 100 yards, the calculations are simple. We know that at 100 yards, one MOA equals about one inch. These measurements translate into raising your scopes aiming point up two MOA and to the right one MOA.
The adjustment on most modern MOA scopes changes the scope by one-quarter MOA per click of the turret. In our example, turning the turret to move the aiming point up 2 MOA takes eight clicks of the turret. Moving the aiming point to the right one MOA takes four clicks of the turret.
Step 4 – Take Three More Shots on the Same Aiming Point
Hold the scope crosshairs on the center of the same aiming point you used for the first group of shots and fire three more rounds. All things being equal, your second shot group should be right on the bullseye.
Step 5 – Fine Corrections
You may need to make some fine corrections to get your shoot group exactly where you want them. At this point, take your time and carefully estimate the corrections you make. Remember that bullets don’t always fly true. Wind, loads, and weights can make a difference in impact points.
Step 6 – Change Aiming Point and Verify your Settings
When you are satisfied with your scope settings, change the point of aim to the next center in your rotation and fire three more shots. Since you must reposition your rifle and scope, this will tell you quickly if your scope settings are true and firing consistently. Hopefully, your shot group will fall back into the bullseye of the target.
Zeroing with a Mil-Dot Scope
The steps are essentially the same if you are shooting a MIL dot scope. Just remember that at 100 yards, your MIL dot scope corrections use a distance of 3.6 inches per MIL at 100 yards, and most MIL dot scopes feature a 1/10 MIL per click adjustment.
Using the matching target will help with this process. The grids marked on the target help estimating the amount of correction. I will tell you from practical experience that using an MOA target and trying to zero a MIL-dot scope only ends in frustration.
First Focal Plane and Second Focal Plane Scopes
To add to the matter, you must understand how your reticle’s location in the scope can affect the use of your scope. Good long-range scopes come in two styles. First focal plane scopes keep the relative reticle size the same no matter what magnification you are using. As your change magnification, the first focal plane reticle changes as well so that the sub-tension markings on the scope reticle are always relative to the target.
Second focal plane reticles maintain the same reticle marking size no matter what the magnification. Since the reticle markings don’t change, you must adjust your calculations to reflect the scope’s magnification. Failing to make these mental adjustments can throw all your windage and elevation calculations out the window.
Which Should I Choose – First or Second Focal Plane?
The choice of which style of the reticle to shoot is a personal preference sort of thing. Finding your comfort zone with your scope is the primary objective. I prefer a first focal plane scope. Since the reticle size is relative to the magnification, I believe it takes extra steps out of my calculations.
However, some people find the reticle changing size a distraction and prefer that the reticle size remain constant despite the magnification. In the end, it is more about personal preference and practicing with your scope than the mechanics.
MOA or MI? What Works for You
The answer to which is better, MOA or MIL, is really about what works best for you. Both systems can produce highly accurate. For most scopes, the scope’s accuracy is not in the reticle, the mechanics, or the mounts. The accuracy of the scope is determined more by the skill and training of the shooter. My experience is that most rifles and scopes can shoot much better than the person behind the trigger.
I hope that this article makes the differences in MOA and MIL scopes a little easier to understand. The principles are much the same. The measurements are quite different. Learning how to use your scope and rifle capabilities is much more important than which style of scope you choose.
If you have suggestions, ideas, or experiences to share, please use the comments section below. Learning is the object of our community, and we are all teachers in our own ways. Remember, be safe and shoot well.