the real truth about mil dots (1)

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The Real Truth About Mil Dots

26 July 2002

By Richard (Rick) Boucher

I have now read three separate articles on the Mil Dot, minute of angle, and thenon-existent difference between Army and Marine Mils.

First what is a mil? It is a shorten name for a milradian. That is it is 1/1000th of a radian. So,what is a radian? "A radian is an angular measurement that is equal to the angle formed at thecenter of a circle by two radii cutting off an arc whose length is equal to the radius." That is adirect quote from the Webster's New World Edition Dictionary. Look at it as a slice of pie in whichthe "outer rounded side" is equal to the two straight sides. The angle at the pointy end is oneradian. How do you find this great angle? OK, radian = 2 pi r/r is the standard formula. So a circlewith a five inch radius becomes (2 * 3.1416 * 5)/5 = 6.2832 radians to a circle of 360 degrees. Bydividing 360 degrees by 6.2832, you find that there are 57.2956 degrees in a radian. You alsoknow that there are 6283.2 milradian in a circle. Either of these can give you the number of

minutes of angle in a milradian or mil. That magic number is 3.438, which is commonly rounded to3.44. This is a mil is a mil is a mil. There is no difference in Marine or Army mils. The problem isthe military compass.

The military compass is marked to show 6400 mils in a circle. The reason behind this I donot know for sure but have been told by numerous sources that is was easier to mark offcompasses in 6400 than in 6283. This is also the source of the myth that the Russians usedifferent mils then the US. Their compasses are marked with a different number of mils in a circle.However, again a mil is a mil. It is based on a set mathematical formula that was used by thescope manufacturers in their marking of the reticles. Leupold marked their mils as mils. There are3.44 moa in a mil. There are no Army and Marine mils. There are only mils.

There are differences in the mil dots however. The Marine mil dot is stamped on wire andthe dot is 1/4 mil length or longwise. The Army dot is etched on glass and is 3/4 of a minute ofangle or .22 mil. While the Marine dot can be easily broken down into 1/8th increments the Armydot can be easily broken down into 1/10 increments. This is very accurate and breaking the milssmaller then 1/8 or 1/10, when ranging with mils, is asking for a disaster and a miss at longerranges. The mils are easily broken down to 1/4 mil increments for leads, wind calls, and holds forelevation or missed shot correction. None of our students have had any real problems withmisidentification of 1/4 and 3/4 mil increments. It is called training.

While I do not know how all of the scope manufacturers make their mil dots, I do know that

all of the scope manufacturers do know what a mil equals. I would be very cautious with the tableshown on one of the articles purporting that some are "Army" dots and others are "Marine" dots.The biggest problem in the Mil Dot arena is the introduction of myth verses reality. Such as thegreat 3/4 mil, mil dot of J ohn Plaster.

Using mils to judge distance is very easy and mils are very flexible for this purpose. Nowthe mil formula works by dividing the size of the target in millimeters by the apparent size of thetarget in mils. This is why the 1000 formula works so well. Size of the target in meters times 1000divided by the apparent size in mils. 1000 is the number of millimeters in a meter. Thus if you havea one meter target and multiply it by 1000 you have converted the 1 meter into 1000 millimeters.


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Now the neat thing about the mil formula is that it assumes that everything is meters and dutifullgives answers in all manner of sizes. Thus if you were to say the size in yards then the answerwould be in yards, if in feet the answer in feet, inches answer inches. Thus a 2 yard tall targetmilled at 4 mils would become 2 times 1000 divided by 4 which equals 500 yards distance. A 6 foottarget milled at 4 mils becomes 6 times 1000 divided by 4 equals 1500 feet which also seems to be500 yards. I could continue in inches but my head is already hurting. This is great for those easyto do times 1000 deals but car tires, tank fenders and a few others may be a bit more problematic.45 inches does not do well times 1000 converted into meters or yards. You can convert 45 inches

into meters but why not simply multiply 45 times 25.4 (number of millimeters in an inch) and dividethat by the apparent size of the target in mils. So now 45 times 25.4 divided by 4 mils equals285.75 meters. For those of you that wish to work in inches you can use 27.7 instead of 25.4. Thistricks the formula into converting the range into yards for you. While this is not perfect, it works.Example is the two yard tall target, 72 inches times 27.7 divided by 4 equals 498.6 meters versus500 yards using the 1000 formula. I can live with the error. When using the mils you must be ableto break the mils into 10ths. This can be done based on the dots themselves. The dots are .22 milbut half is .11 mil. Using this information you then rest the target on the top or bottom of a mil andthen measure up. Say, top of one mil to bottom of second mil and the reading is 1.8 mils. Anotherexample would be bottom of one mil and top of second mil and you have 2.2 mils. Combinationsof the above will give you anywhere in the tenth scale.

The standard for milling the human body is the crotch to top of head in conjunction with theshoulder to shoulder measurement. Using smaller than this and be accurate, and you will be inthe 6 inch point blank zero range anyway.

Mils can also be used to hold for winds and it is taught that way in SOTIC. Dialing on windscan be a disaster when you have only seconds to engage in changing wind situations. The milswill hold at 1/4 mil increments easily which is just smaller then 1 moa or .86 moa. This will get youa hit and if you were real anal, then a light 1/2 mil would be 3/8th of a mil or .43 moa. To me this isjust too anal. Wind calls are taken from the center of the target as a standard reference point.

The Mil can be used very successfully in holds for elevation. With the criteria of bullet pathbased on a 500 meter (or yard) zero, the sniper can place 500 on his scope and hold for anytarget from push the barrel through his guts to 700 meters. We use this info for our students andgive them a standard chart that contains that info. That info is only good for the M118 SB and theM118LR. However, anyone can reconstruct one for his or her particular bullet. You are merelycompensating for bullet path within the scope. As an example the shooter would hold 5 mils lowfor a 100-meter shot with 500 meters on his weapon. He would also hold 1 mil high for a600-meter shot with 500 on the weapon. The usual problem is that the shooter must hang thetarget in space for long shots while holding for elevation AND wind.

The mil can also be used for engaging moving targets and here the best practice is to use

the leading edge for a trigger point. This is due to the problem of shooters looking at the target tofind the center of the target. We have our students use the leading edge to stop this problem.There are three general methods of target engagement with moving target. One is ambushing ortrapping. We use this method to teach new students moving targets. Another is tracking and issimilar to the quarterback pass. And the third is a combination method. In any of these methodsthe leads are called in mils based on the leading edge of the target. Engaging movers past 400meters becomes a pain due to wind considerations. Again mil dots will help. As an example, saythe lead for the moving target is 2 mils and there is a 3/4 mil wind. Now if the target is moving intothe wind then the lead would be two mils PLUS the wind of 3/4 mils so the observer would give alead of 2 and 3/4 mils. However if the mover is moving with the wind then the wind is subtractedand the lead becomes 1 and 1/4 mils. Fun huh!


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Well this is a quick down and dirty and hope that it clarifies some of the info put out insome of the other articles floating around.

Now that you've read this, click here to see a 16-slide show explaining the above.

(Unfortunately th is works wi th Internet Explorer only.)

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