No math involved: April 30, 2008

What else can you use the mil dot reticle for? Well, if you are shooting in a crosswind, you can use the dots as additional aim points to compensate for wind drift. If you notice the strike of your pellets in relation to the dots, you can aim off to one side by placing a dot along the horizontal reticle over the target instead of the crosshairs. By choosing the correct dot, you can easily adjust for how much the pellet will drift in the wind and end up with a perfect shot every time. Better still, there is no math involved! Dirt E. Harry

Rangefinding reticles: April 29, 2008

Military binoculars and gunsights are usually equipped with mil reticles. On the standard crosshairs are other short lines that mark mill angles. These are often referred to as rangefinding reticles. To use them that way, you have to know how to apply the correct mathematical formula, plus you have to know the approximate size of your target. Dirt E. Harry

Height and Width: April 28, 2008

Sniper rifles have mil dots on both horizontal and vertical crosshairs so they can measure height as well as width through their scopes. A six-foot tall man is also 72 inches tall. At 100 yards, he would appear to be just over 20 mils tall. At 1000 yards, he would be close to 2 mils tall. Dirt E. Harry

Target distance: April 27, 2008

If your bullseye is 3.5 inches in diameter and 100 yards away, it will touch the centers of any two dots next to each other. If it appears only half that size through the scope (from the center of one dot to half the distance to the next center) your target must be about 200 yards away. If the same bullseye spans the distance between the centers of three dots (two with an extra dot between them), your target is about 50 yards away. Dirt E. Harry

Now what is a mil? April 26, 2008

One mil of angle is approximately 3.6 inches long at 100 yards, and that is close enough to 3.5 minutes of angle to be convenient. In Leapers mil dot scopes, the centers of the dots are one mil apart. If the scope is variable power, this only holds true for the highest power setting. Dirt E. Harry

A mil dot reticle does not refer to the military: April 25, 2008

First, we have to know what a mil is. A mil dot reticle does not refer to the military. The MIL in mil dot is a shortening of the term milliradian. You are familiar with degrees as measurements of angle. You also know from high school geometry that there are 360 degrees in a circle. As the circle grows larger in circumference, the number of degrees does not change, but the distance between each degree along the circle does increase. You may also know that degrees are divided into smaller units called minutes. There are seconds, too, but they are too small for this discussion. A degree is divided into 60 minutes. At 100 yards distance, the angle of one minute is approximately one inch. So if the centers of the two bullets farthest apart in a 100-yard group are about one inch apart, we call that a minute-of-angle group. Get it? At 200 yards, a group measuring two inches center- to-center equals a one minute-of-angle group. At 400 yards, it’s a four-inch group. At 50 yards, it’s a half-inch group. Dirt E. Harry

What is a Mil-Dot scope?: April 24, 2008

Next, is an article by Tom Gaylord who again is probably theee authority on air guns. Tom has forgotten more about air guns than most of us will ever know. First of all, we have to know what a “mil” is…. Dirt E. Harry

Do you REALLY NEED AO?: April 23, 2008

Well, no, you can get by without it, if need be. In fact, you can get by with open sights, if a scope isn’t in your budget. But, if you are contemplating a future scope purchase, I recommend that you consider saving a little longer until you can afford a scope that has AO. It makes your shooting that much better!

In the meantime, until you get a scope with AO, here is what to do. Practice mounting the rifle in the same way every time, so your face contacts the stock at exactly the same place, shot after shot. That way you will reduce whatever parallax error your non-AO scope has, and you will get the best accuracy possible under the circumstances. Dirt E. Harry

Ranges are not always exact: April 22, 2008

Temperature affects optics by making them expand or contract. Since optical tolerances are measured in units smaller than one-millionth of an inch, any change in dimensions will affect how the optic works. In the case of parallax correction, the scale of yards will change with the temperature. So the number 20 on your AO scale could really represent 19 yards today and 23 yards next week, if the temperature fluctuates that much. Field target competitors compensate for this change by having three different color-coded range scales on their adjustment wheels, but you don’t need to. Unless you are concerned by your pellet striking one-tenth of an inch away from the aim point at 30 yards, the scale on your parallax ring or wheel is good enough for all shooting. Just understand that the measured distance will not always be the exact distance for this reason. Now you know what AO stands for. Even though many scopes with parallax correction are now using side adjustment knobs, the marketplace still uses the term AO to mean all scopes with parallax correction. Dirt E. Harry

Sidewheel adjustment knobs: April 21, 2008

The sniper scope builders also borrowed something else from airgun scopes, but as yet they have not developed it fully. That feature is a side adjustment knob for parallax. The location makes adjusting parallax easier because the shooter doesn’t have to reach all the out to the end of what is usually a very large scope. The adjustment knob is on the left side of the turret, opposite the windage adjustment knob. Airgun scopes had this feature back in the early 1990s (which is why the term AO isn’t always correct – but who cares?), and ten years ago, shooters began experimenting with the size of the adjustment knob. Dirt E. Harry