If you’ve looked into long range shooting, which for our purposes means anything beyond a few hundred yards, you’ve probably come across the terms Minute of Angle and Milliradians, or MOA and Mils when looking at rifle scopes.
These are very important concepts to understand if you’re going to be doing any long range precision shooting or hunting. They’re especially important if you want to participate in any of the long range precision shooting “games” or competitions like the Precision Rifle Series.
We’re going to go over what these terms mean, and how understanding them can help you become a better shooter.
What are MOA and Mils?
Minutes-of-angle and milliradians are both angular units that measure angles within a circle. These take some trigonometry to really understand, but that’s a little bit beyond the scope of this article. We’re going to focus on practical application today.
For practical purposes, MOA and Mils are used to adjust your scope and zero, estimate windage, compensate for bullet drop, and gauge accuracy. Understanding one of these measurement systems will help you shoot better, and be a more versatile hunter or competitor.
Learning how these two measurements work will open up a new world of precision shooting to you, and will really go a long way towards making you a more complete rifle shooter. These are two very important tools for making shots at any kind of range.
The reason MOA and Mils are so important in this context is that they are used to measure the angle between where your barrel is pointing vs where your bullet lands.
Imagine you’re shooting a space-age laser rifle instead of a gunpowder-fueled rifle. A laser beam would travel straight from the end of your muzzle to the target with no drift left or right, or drop.
We don’t quite have laser guns yet though, so we have to deal with things like bullet drop and windage drift. MOA and Mils help us to measure these things with respect to where the muzzle is pointing, and help us to gauge where we actually need to point our muzzle to hit the target.
You can also do some conversions that will tell you how how high or how far from left to right you’ll need to hold in inches to compensate for wind and bullet drop, as well as some conversions that will give you the distance to a target of known size provided you have a Mil or MOA reticle that gives you angular measurements.
So what exactly is a minute of angle? A minute of angle is 1/60th of a degree, or for our purposes here, 1.047 inches per 100 yards. So a rifle that shoots “sub-MOA” will manage a less than 1” group at 100 yards, less than 2” at 200 yards, etc, provided a shooter is equal to the task.
The reason you see MOA scopes is because MOA have a very easy translation when ranging a target at unknown distance, especially if you’re used to US measurements. One MOA is slightly less than 1″ at 100 yards, 2″ at 200 yards, etc, and that makes for an easy (if slightly inaccurate) frame of reference.
For practical purposes, you can just assume that MOA is 1 inch per 100 yards, and if you have a MOA scope with ¼ MOA adjustments, you can adjust accordingly. This will give you a practical accuracy that’s more than sufficient for plinking or hunting.
If you have a scope that’s got vertical hashmarks for every MOA, and you have a whitetail buck, which you know is about 18” from belly to back, you can use your reticle to find out exactly how far away it is.
You can actually do this with any target of a known, or at least closely estimated, size, by measuring its relative height through the scope.
Note: if you have a first focal plane scope (FFP), this works at any magnification, if you have a second focal plane scope (SFP) this only works at the highest magnification your scope is capable of.
If you have a hash mark for every MOA up and down and left and right along the crosshairs in your scope, and the deer measures three hash marks from the top of the back to the bottom of the belly, the dear is 3 MOA tall.
To convert that to distance in yards, take the height in inches (18) and divide it by the height in MOA (3), and then multiply that number by 95.5. For our example here, that gives you 573 yards from you to your deer.
Now, you can plug that number into a ballistic calculator, or consult your dope card to see exactly how many MOA you need to holdover the target, or how much you need to adjust your scope so you can hold dead on.
A milliradian is an angular measurement, just like MOA is. Its equal to 1/6400th of a degree, or 3.6 inches at 100 yards. This larger unit is why Mil scopes adjust in 1/10th of a unit and MOA scopes adjust in ¼ of a unit, but they’re still about the same adjustment size.
You can do the same sort of ranging with Mils that you can do with MOA. To get the distance to a target of known size with a mil scope, you can divide the height of a target of known size in yards by the measured height in Mils as seen through your scope’s reticle, and then multiply this by 1000.
So, say you have a deer that you know stands about a yard tall at the shoulder, and it appears to be 4 Mils tall in your scope. 1 divided by 4 gives us .25, and then multiplied by 1000 we get 250. Your deer is 250 yards away. Adjust accordingly, and make your shot.
Which is Better?
Which system is better?
Honestly, neither. Milliradians are typically more intuitive to use, but you can use either system with equal effectiveness provided you’re being precise in how you go about it. If you’re a new shooter, I’d recommend you use mils for this reason, and because its more popular in general with the long-range precision crowd.
If you’re already more comfortable with MOA ranging and conversions, keep using that.
There are a few things you should keep in mind though.
Things to Remember
First and foremost, if you have a MOA reticle, make sure the scope also has MOA turrets. Same with mils. Mils to Mils and MOA to MOA eliminates the need to do a mils to MOA conversion or vice versa. You’d think all scopes would be one or the other, but there are a frankly stupid number of manufacturers that mix the two.
Next, try to get away from worrying about inches or yards or feet or whatever in terms of adjustment. For ranging, this is fine. If you need to know how far away something is, use these terms.
But for adjusting for impact, try to use MOA or mils as measured through your scope. If you’re shooting a target against a berm, and you miss left, don’t try to guess how far off you were in inches or feet. Use your reticle to measure and adjust from that number. Don’t try to guess in inches and convert to an angular measurement, especially in the field.
Finally, if you’re going to be doing hunting or competition shooting with your scope, learn some target sizes and some formulas. The numbers I gave you for whitetail deer are pretty solid, and that’s what I have used to bring home literally tons of venison over the years.
If you’re a competitor, know some standard target sizes. For example, a full-sized IDPA target is 30 inches (.83 yards) high, and is 18 inches (.5 yards) wide. Beyond that, learn some ranging formulas you can easily remember, and make a card or memorize your scope adjustments or holdovers for certain ranges with the ammunition you use.