The Truth About Mil Dots

By: Michael Haugen © 2001

Anyone associated with snipers and sniping is familiar with Mils and Mil dots. However, it seems that there is a substantial amount of confusion regarding their origin, limitations and employment. 

Before I begin I must admit that most of the technical aspects of the proceeding is the courtesy of Chris Thomas of Premier Reticles LTD. They have done extensive research on this subject and currently are responsible for the Mil-dot reticle in the USMC Unertl optics as well as the retrofit Mil-dot reticles for Leupold. So Chris if you read this please forgive me for plagiarizing you. 

The term or measurement of Mils (or Milliradian) is a trigonometric function used to configure and use the Mil-dot in estimating range. Here are the specifications.

1 Milliradian = 1/1000 th of a radian, 1 radian = 2 PI

1 Milliradian = .0573 degrees or 6283 parts of a circle

Earlier this century, the Infantry used Mils to correct the trajectory for indirect fire and crew served weapons mainly because Mils were finer than degrees and enabled them to be more accurate. The Infantry divided a circle into 6280 parts or 1/6280 th = 1 mil. This was a slight deviation from the truth but was close enough and made it easier for them to compute and work with. Shortly thereafter the Artillery took notice of the system and decided to refine this system even further and rounded the number to a even easier number, 6400 mils to a circle or 1/6400 = 1 mil or 17.8 mils = 1 degree. This system stands today and is widely used in all services.

 When the Army decided to incorporate a range estimation tool into it sniper optics it chose this system and had Leupold make the reticle accordingly. I should clarify this point for those out there not familiar with the Leupold M3 Ultra currently used by the US Army. Many people believe that the Mark IV M3 that they see advertised by various retailers is the same as the optics on the Army M24. Although they are identical in appearance, they are not the same. Specifically the reticles are different, the M3 Ultra uses a etched glass reticle with round or Army mil-dots, whereas the available Mark IV M3's sport a Premier wire reticle with the USMC oblong dots. I can imagine that there are a few people saying what is the difference? about now. Well let me expound and all will become clear (like muddy water).

 Since I have gotten to this point let me cut to the chase and present you with the math that accompanies what I have already said.

ARMY: 360 degrees = 1 circle
   6400 mils = 1 circle, 360
    17.8 mils = 1 degree
   360 degrees divided by 6400 = .0563 multiplied by 60 = 3.375 MOA or
1 mil = 3.375 moa

USMC: 360 degrees = 1 circle
   6283 mils = 1 circle
   17.5 mils = 1 degree
   360 degrees divided by 6283 = .0573 multiplied by 60 = 3.438 MOA or
    1 mil = 3.438 moa

Therefore:
ARMY: 3.375 moa multiplied by 1.047 = 3.53 @ 100 yards
USMC: 3.438 moa multiplied by 1.047 = 3.6 @ 100 yards 

** Note: 1 Minute of Angle = 1.047 @ 100 yards (True) 

While we are distinguishing between Army and USMC reticles, I feel it is prudent to mention another difference. Not only are the mils themselves different but the value of the dots is also different. Army dots while commonly called ¾ mil dots are in reality ¾ moa dots (or .22 mil). This is to say that 1 dot subtends (covers) three quarters of a minute of angle or .75 inch at 100 yards. The USMC dots are ¼ mil dots (or .86 moa) from edge to edge. Each USMC/Premier oblong dot subtends .86 at 100 yards. Now I suppose someone out there is wondering what this is all about and what difference does it make. Well, it makes a greater difference at longer ranges but in the immediate future, it has a great impact on how the optics is used. 

With Army dots, a quarter mil (1/4 mil) is the width of the dot from edge to edge plus the width of the line. As you can see from the diagram the ½ mil, ¾ mil and 1-mil locations are depicted. The commonly missed identified are the ¼ mil and the ¾ mil. 

USMC dots, the measurements are easier to identify and remember.

 I am sure that all of the above is somewhat confusing but, you have to remember that the mil-dot system merely provides aiming reference points and a range estimation tool. Where the actual locations of the ¼, ½, ¾ or 1 mil point are depends on where your starting point is. What I have drawn above gives you the quick reference points. If you are set on using center - center or edge edge starting points then you will have to find those subsequent points. The bottom line is two fold. One, know what the values are of the reticle you are using. Two, use the same points all of the time. Do not get wrapped around the axle about what is best (edge to edge or center to center), just pick which ever one is easiest for you to use. 

Now, what does all of this mean? Well it means that depending on the reticle you are using, you must understand the math associated with it. In some cases you may be using both systems and therefore you must be versatile enough to make the translation. 

One of the problems is that all of the reference material available today does not make the distinction between the two reticles and assumes the reader is knows which system he has (and that there is a difference). The US Army manuals, TC 23-14, FM 23-10, and ST 31-20-4 all use the round dots, while the USMC manual FMFM 1-3B uses the oval dots. Civilian reference like John Plaster's Ultimate Sniper which plagiarizes several manuals uses the Army dots as his example. Additionally, optic manufacturers do not always tell you how to use their reticle. Here are some optics and the reticles they use. 

Of course, there are several others but this should give you an idea.

Let's get to the meat and potatoes of the issue, which is how to employ a mil-dot reticle. Of course, most shooters know that the mils are used for basically two reasons, to estimate range and to hold for wind. First, we will look at the more important of the two, range estimation. I have read many articles on using this system, everything from reprints of the service manuals to someone's personal interpretation. Here is what we teach in the Army. First when mil'ing humans the mil will be derived from the crotch to the head, not from feet to head. The reason for this is that the majority of people's height is derived in the legs not the torso. The common human torso is approximately 1 meter (39) from crotch to head. Now before I get hate mail about this issue, let me say that for field snipin g this measurement will suffice. I usually use either the center of the reticle or one of the heavy posts as a starting point, it is easier to hold and therefore read. Once the starting point is set then look up and read the mil's. Mil's need to read to the 10 th of a mil (ie. 1.6, 2.3, etc) in order to be accurate, which by the way is the point here ACCURACY. Estimation of range is the hardest skill a sniper can acquire. There are areas where the sniper can swag (scientific wild ass guess) something but, range estimation needs to be as accurate as possible. Once you have the mil reading then you plug that into the formula.

1000 = range in meters
mils

A word here about meters verses yards. We normally use meters, however you must be able to calculate the difference. As I have said you can (and should) mil humans from crotch to head but you can also estimate range by mil'ing from shoulder to shoulder and side to side of the head. CAUTION HERE, never use the shoulder to shoulder method on targets past 600 meters and NEVER use the side to side of the head past 400 meters. In reality the side to side should only be used close up or when there is absolutely no other target available. While on that note, let me mention something else. I have read articles where people are talking about mil'ing targets out past 1500 meters. Just let me say that mils are extremely difficult to read on humans past 1000 meters from 10x optics. Higher power optics will increase this range somewhat but mirage and environmental conditions will make readings inconsistent and unreliable (note: the mil-dot reticle must be made to function at the desired power if using a Premier Reticle). The formula for mil'ing from shoulder to shoulder and side to side of the head is as follows;

500 = range in meters **Shoulder to Shoulder method
mils

250 = range in meters **Side to Side of the head method
mils

Okay, we have discussed using the mil-dot reticle against human targets and at this point it is relevant to mention that the mil-dot reticle can be used to determine range using other items as well. First, you must know the height or length of what you are measuring. As noted above we used the number of 1 meter as a standard and 1000 as a constant. If you are measuring something that is 2 meters (78) than the constant would be 2000. If the target was say a varmint about 10 high (9.75) you could use 250 as a constant. You can do the math for anything else you are trying to determine range.

Now onto the next subject, holding off for winds. Like most subjects in sniping, a lot has been written about winds. Normally determining wind speed is the subject of the article and the result is a dial on solution. With the mil-dot reticle, you can hold off for the winds in increments of usually ¼ mil. Anything smaller that ¼ is too finite to really deal with. Now I know snipers (usually students, me included) who use things like light and heavy ¼, ½, ¾, and 1 mil. For one thing this measurement or aiming point is not definable, two what exactly is a light ¼ mil? It is either ¼ mil or it isn't. Another thing is that in sniping we generally accept a 2 moa standard for the weapon, shooter and ammunition in existing environmental conditions. That is to say that in any given situation the sniper should be able to hold 2 moa. So, what is the difference between a ¼ and a ½ mil? The answer will come back a hit or a miss. While that is true a lot of the times, it usually a function of shooter error rather than a bad hold or call. What I mean is that if the rifle were benched and fired using a ¼ mil hold and then a ½ mil hold the result would not be enough to miss (1/4 mil is 1 inch at 400 yards). Back to the wind holds. Once you have determined the wind speed you can easily convert that to a mil formula and use that as a hold. Of course the best answer is to figure that all out before hand (or just get the chart) and have it available for reference. Before anyone gets too excited, this of course will be dependent on the caliber, bullet weight, velocity, range, wind speed and direction. If you have figured out the minute of angle value for specific winds using your specific weapon/caliber you can convert those figures (best method) into mil hold offs. The last part of this particular aspect is that ALL HOLDS ARE TAKEN FROM THE CENTER OF THE AVAILABLE TARGET. Not from the leading edge or anywhere else. This primarily due to standardization between the shooter and spotter, which I will go into shortly.

Next is using the mil-dot reticle for holding off for elevation changes. Same technique is applied here. Once you have figured out the elevation changes for various distances you can convert them to mils and use the reticle to hold over or under. A word of caution should be given here. As you know the longer the range the more exact the call and hold has to be, so it should be understood that mil hold overs should NOT be use at extended ranges usually exceeding 700 meters. This technique is best used in conjunction with a point blank zero (my previous article) such as 500 meters (or yards). What this will do is allow the sniper to engage targets from approximately 175 meters to approximately 700 meters. Again a note of caution, this is for military snipers who can use it to suppress targets. Obviously, this system is NOT inherently accurate or capable of precision target engagements.

One of the more useful aspects of the mil-dot reticle is that of engaging moving targets. This is done by incorporating leads, which then (just like shooting skeet) are used to engage a target. Without going into the leads themselves, the mil-dots allow the shooter to establish a definable aiming point for which to engage the target. There are several aspects that must be considered here when engaging moving targets. The first is target speed. Typically people will walk, jog, run or sprint. This makes target speed determination extremely difficult, especially if there is a considerable distance involved. Of course, the best answer is to wait until the target is stopped, but if that isn't an option then leads will have to be used. The second aspect is terrain. If the terrain is uneven, the target will move up and down again making the shot difficult. The next item is masking or vegetation through which you bullet will have to pass. If the team is in a hide with moderate vegetation between them and the target, then tracking and engagement will be extremely difficult. The last aspect is environmentals, namely wind and temperature. If there is substantial wind then the lead will have to either be added to or subtracted from the lead. It is possible to have to hold behind the target in order to hit it. The end all here is that if you are in the business that may require engagement of moving targets of any and all varieties, then you have to practice in like conditions (sounds familiar doesn't it?).

Finally, this article is ending. The last subject connected with the mil-dot reticle is shooter spotter dialogue. This is the single most important aspect of sniping. I have seen excellent individual snipers who when teamed together could not function. The team's dialogue must be understandable to both members, complete, short and concise. If you are a part of unit in which you may have to work with a variety of snipers or spotters then it is extremely important that there is a standardized dialogue within the unit. The basic elements of the dialogue are;

1. Warning (alerts sniper or spotter to possible action)
2. Target location (short and methodical)
3. Target description (short but detailed enough for the other to identify)
4. Target status (what is the target doing)
5. Distance determination (a variety of methods, military spotters will issue mil's?
6. Range confirmation (either confirmation through secondary system or re-milling)
7. Index (sniper either dials range on or prepares to hold)
8. Wind call (spotter determines wind speed and direction and tells sniper to either dial it on or to hold)
9. Fire command (usually this is automatic after the wind call, if the sniper hasn't fired within 9 seconds the spotter gives hold and recalls wind)

I guess I have said enough about this issue. I hope this benefits someone out there (good guys). As anyone knows who deals with this profession, regardless of the equipment, methods or techniques a sniper must practice and practice often. Most shooters spend all of their training time on a range shooting paper. Although this is needed, snipers must train in all of the other aspects and none are as important as range estimation. Let me close on this note, laser range finders and all of the other whiz bang gadgets are nice but what will you do when the batteries go dead?