By now most of us have probably at least heard of these mystical little creatures that reside on the reticles of military and law enforcement snipers around the world. Tasco has made them suddenly affordable and as a result, a lot of people are starting to throw them on top of their bolt guns without understanding their full potential. What I'm going to try to do in this article is explain how to use the mil-dot reticle to determine range, leads for moving targets, and a little on their application for windage and angle shooting. I'll try to do this in a way that won't put you to sleep, or quickly deteriorate into memories of your high school math class. Don't misunderstand me, using these things effectively and to their full potential is going to require some math ability, not much more than long division and multiplication, but it will be there. Before going any further, the mathematically challenged (as well as the rest of you) among us may want to open the calculator program on your desktop.
Before I get too complicated, allow me to give you a little history. "Mil" is short for milli-radian, which is nothing more than a measurement of an angle. Most of us know that there are 360 degrees in a circle, and 60 minutes in each of those individual degrees. Likewise there are 6400 mils in a circle (17.7 mils per degree). This breaks down even further into approximately 3.5 minutes of angle per Mil. (One Minute of Angle (MOA) is equal to 1" at 100 yds, 2" at 200 yds and so on) That's the important part- 3.5 MOA=1 Mil. Remember that if nothing else, and you'll be ahead of most of the populace who has them "....because snipers use them and snipers shoot good, therefore having these dots in my scope will make me shoot good as well.". Don't laugh (well, a chuckle is okay), you'd be surprised what some people will believe.
The first (some will say most) important aspect of long range shooting is being able to accurately judge the range to your target. Reason here is that as we start stretching the distance, our bullet will drop at a steeper and steeper angle. This makes it even more important, the further the range. Unfortunately it also makes it tougher for the eyeball to do it accurately. For example (I'll use the .308 Win in all my examples unless otherwise stated) at 800 yds the .308 Win (shooting a sierra 168 gr. HPBT Match bullet at a muzzle velocity of 2725 fps with a 100 yd zero) drops just over 24.5 MOA or approximately 196 inches. While an identical bullet at 850 yds drops just under 29.25 MOA or approximately 234 inches. This means that misjudging the range by only 50 yds - an error of only about 6 % will result in a difference in point of impact of over 3 feet! This could easily make the difference between a center mass shot and shooting between your target's legs. No doubt this will scare him, but it's definitely less than lethal.
Enough on the why, here comes the how. Keep in mind that on variable power scopes your mil-dot will only be a true mil-dot at a certain given power (usually this is the highest setting, but never assume). I know that the little sheet that comes with the Tasco says how you can utilize the mil-dots at different powers, but you'll save yourself some headaches by either using it as a true mil-dot (where 1 mil will equal 3.5 MOA) or simply not using it at all. Pay attention now, there'll be a test at the end. The formula for determining range is this:
Size of the Target (measured in yards) X 1000
Size of the target in Mils =Range to the Target in Yards
Here's a quick example to walk through. You know your target is 18 inches wide (to convert this to yards simply divide it by 36). The result is a target 0.500 yards wide, which we multiply by 1000 (This gives us 500 on the top line of our formula). Now looking through the scope we see that our target covers the area between the left sides of two dots almost completely. We estimate this to be 8/10ths of one mil. We now have
a formula that should look like this:
.8 = The range to our target in Yards (In this case 625 yds)
**Remember that 1 mil is the left/right side or center of one dot to the same corresponding side or center of the next dot. The point where the crosshairs intersect would be the center of a dot if there were one in the middle.
One Mil One Mil One Mil
Okay, hopefully everybody is still with me here. The next thing covered would normally be windage, but that depends on the caliber, velocity, type of bullet you're using, etc. so any formulas I give will be wrong to someone. Therefore, I'm leaving most of the windage discussion out. How you can use the mil-dot in this situation, is simply as a more effective hold point than guessing. For example if your target is at 500 yards, and you know you'll need 7.0 Minutes of windage (for your particular bullet). Well, look at that- how convenient, since we know that 1 mil=3.5 MOA we can simply hold two dots off (which side we'll hold obviously will depend on wind direction) and shoot. For all you .308 shooters here's the formula:
Range (in hundreds of Yards) X Wind Velocity (in MPH)
Range Constant =Minutes of full value wind
The range Constants are:
100-500 yds - 15
600 yds - 14
700-800 yds - 13
900 yds - 12
1000 yds - 11
The key there is the full value part. The answer you get will only be accurate if the crosswind is perpendicular to the shooter/target line. If it's not, you'll have to account for this when determining the correct amount of windage to use.
Okay (apologies to all the non-.308 shooters that had to read through that) moving on, the next area that the mil-dot becomes useful is in determining and shooting the proper leads for moving targets. Since it will take the bullet time to make it downrange, a moving target will have since departed its original position when the bullet arrives. We are simply going to compensate for this by anticipating where the target will be when the bullet arrives. This won't be much use for a deer at 35 yards, but it works great on people walking around at 600 yds. This is actually a two step equation, and the first thing we need to determine is how much lead (measured in feet) we will need to hit our target. Simple formula on this one:
Time of flight X Speed of the target (in FPS)= Lead in feet
Easy enough right? Now we start to get weird, to convert this into something we can use with our mil-dot reticle, we have to do this:
(Lead in feet X 12) - 6__
Range (in hundreds) X 3.5 = Lead in mils
I can explain it if anyone really wants to know, but just take it at face value, and know it'll work just fine. Let's run through an example real quick. A man is walking along at 4 feet per second out there at 800 yds. Our time of flight for a .308 shooting M118 Special Ball is 1.23 seconds at that range. Therefore our lead in feet is:
(1.23 X 4 =) 4.92 feet. Rather than trying to eyeball 5 feet at 800 yds, we use part 2 of the formula like this:
(4.92 X 12) -6
(8 X 3.5) =Lead in mils
28 = Lead in mils
28 = 1.89 This is our lead in mils. We can eyeball what is just short of 2 mils pretty easily inside the scope. We move our scope out in front of the target, and fire just as he crosses that 1.9 mil mark. Hoping that he doesn't change direction or speed on us, our bullet will arrive at the same point in space at the same time our target does. Not too bad for a moving target only 10 inches wide and 1/3 of a mile away is it? Keep in mind that this formula, as with the windage, is only correct for a man walking perpendicular to the bullet's path. If he is quartering toward or away, this must also be accounted for.
The next part I'm going to mention really could've been covered in the first part of this article but I've left it until now because I'm the author and I can do that. Most of us have probably heard that if you shoot up or downhill you have to hold high/low/left/right or turn the rifle upside down to hit where you want. Here's how it works. Imagine a right triangle with you at the top of the right angle, and your target at the end of the opposite ray.
Actual Range to the target (750 yds)
You're shooting along the longest axis of the triangle, and the range you estimate will reflect this. The problem arises because gravity exerts its forces perpendicular to the earth (take it up with Newton guys, this is just how it works) and therefore gravity will only be pulling on your bullet for the length of the (shorter) base of the triangle. The solution is easier than it seems. Get a protractor and a weighted string. When the rifle is on target use this to measure the angle. Unless you're in a city, or do most of your shooting from a hot air balloon you probably won't exceed 15º of angle very often. I did most of my training on this in the Sierra Nevadas, and the mountains of Southern California, so it wasn't rice paddy flat by any means. All you have to do is this:
Range to Target in Yards X Cosine (for the appropriate Angle of the
The range you'll need to put on your Scope
Here's the example to go with the above picture:
We mil the target out and come up with a range of 750 yards to our target. The angle is 15º (The cosine of a 15º angle is .96) We multiply 750 by .96 and get 720 yards. Although the range from us to the target is actually 750 yards, the bullet will impact at the point it would hit if the target were only 720 yards away. For the .308 this is a difference of 18"- enough to matter? Absolutely. Were we to increase our angle to 30º (a pretty steep angle) the bullet would impact the same point it would normally hit at only 653 yards (A whopping 54" too high). At longer ranges this is obviously enough to cause a miss by itself, but where it also affects us is in the initial range estimate if we have to mil our target out vertically, which is sometimes the only option. Because of this, it's recommended to use a horizontal mil reading as much as possible, and use the target width rather than height in the range estimation formula.
Why this becomes a factor is because now we have to consider the distortion caused by viewing the target at an angle. To illustrate this better, take a pencil and hold it vertically with the bottom on a flat surface at eye level. We know the pencil (our target) is 6" (6 feet) tall top to bottom. If you tip the pencil toward you (simulating shooting at an angle to it), you see that it now appears shorter even though its height hasn't changed. Since we know its height to be 6" or 6' the angled view causes the target's image to cover less mils in our scope which throws the whole equation off. All we have to do here is multiply our estimated range to the target by the appropriate angle's cosine Twice. The first time compensates for the angle itself, and the second time we compensate for the distorted view of the target. In the above 750 yd 15º example, if it were a vertical mil reading we'd used to determine the range we would have to multiply our answer of 720 yards once more by .96 to give us a range of 691.2 yards. That's 16 inches of adjusting all because of a distorted view. All we do to fix the problem is use the appropriate come-up to hit at 690 yds on our scope and take our shot at the target (at 750 yds). You'll be amazed at the results....
If we had used a vertical mil reading to estimate the range, and had not considered this or the angle of our shot into the equation, our shot at the target would've gone just over 34 inches high. I'd have to bet your target isn't nine feet tall, so unless you were trying to neuter him, that shot was a clean miss.
**One thing that bears mentioning here is that the angle of your shot will not affect any windage adjustments you need to make. The windage to keep this shot on target would still apply at its full 750-yd value. Not the reduced value needed for elevation.
Here are the cosines in 2.5º increments to cover all the possibilities.
0º-1.00 2.5º-.995 5º-.99 7.5º-.985 10º-.98 12.5º-.97
15º-.96 17.5º-.95 20º-.94 22.5º-.925 25º-.91 27.5º-.89
30º-.87 32.5º-.845 35º-.82 37.5º-.795 40º-.77 42.5º-.735
45º-.70 47.5º-.67 50º-.64 52.5º-.605 55º-.57 57.5º-.535
60º-.50 62.5º-.46 65º-.42 67.5º-.38 70º-.34 72.5º-.30
75º-.26 77.5º-.215 80º-.17 82.5º-.13 85º-.09 87.5º-.045
Now, I'm going to answer those of you out there asking, "Well this is all very nice, but who the heck has the time to do all this in the field, when the deer is running away, or the target only exposes itself for a minute?" The answer is nobody. It's not realistic to expect to use any of this information on a running deer or similar target. These are Sniping formulas used for Sniping. That is, taking one carefully selected and prepared for shot, often at long ranges and having an exceptional chance of making that shot connect. If the target only appears briefly, fine- you can have all of the math done before he appears, and make your shot when he does. If you're walking around when you notice your target- you're in NO position to make the shot in the first place, so find a spot, do your math and wait. Contrary to popular belief, sniping is not just climbing a tree and shooting away at anything you want.
The reason I prefer the mil-dot over other types of reticles is that it will work for any caliber, and all the math stays the same. If I were to take the scope off my .308 and put it on a .223, or a .50 BMG. The results would be the same. I could still use all the formulas above to get any information I needed to make a shot. Also in regards to the range estimation feature of many scopes, I can determine the range to anything, by knowing the targets approximate size with a mil-dot. I don't have to search for something 6" or 9" or 18" tall in the area of my target, and memorize what size target I'm looking for depending on which rifle I'm carrying to make a shot. I've also spent a lot of time in the service using these scopes so the familiarity factor is a big reason in my choice. Overall I just believe the mil-dot reticle to be more flexible, and I believe flexibility to be an important factor in a world ruled by Mr. Murphy. That ought to be enough to get some of you started, scare others away, and confuse the ones who used to understand this stuff. If anybody has any suggestions, comments or would like to see anything further in this area, feel free to drop me an e-mail. Remember, if it's stupid, but works- it ain't stupid. Use what works best for you.
Legal disclaimers, blah, blah, blah, if you use this information to shoot folks from a water tower or book depository, it's neither my fault nor that of the weapon you're using, etc. etc. something about informational purposes only and all that stuff.
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