MOA dot sizing

MOA dot sizing

This is a discussion on MOA dot sizing within the Defensive Rifles & Shotgun Discussion forums, part of the Related Topics category; I ran a search here and came up dry, Google is unhelpful at this time as I am at work and all the good sites ...

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Thread: MOA dot sizing

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    JD [OP]
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    Question MOA dot sizing

    I ran a search here and came up dry, Google is unhelpful at this time as I am at work and all the good sites come up blocked.

    Can some more insightful individuals break down MOA dot sizing as to what "sizes" fit what application.

    I am currently investigating Aimpoint red dot sights and am considering a Aimpoint Comp ML2 with a 4 MOA dot for my SOCOM 16.


    Thanks in advance for any feedback.


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    http://en.wikipedia.org/wiki/Red_dot_sight

    I had a 5 MOA red dot (el cheapo from Famous Maker $29.95) on my FAL. At 100 yards it could cover up a basketball. I took it off and put a 3x power 40mm compact scope on instead.

    For 50 yards and less the 5 MOA was great. But for my FAL I wanted a greater degree of accuarcy at longer ranges. When I finish my AR build I am going to spend the money and get a 3 MOA Red Dot.

    I hope this helps
    “You can sway a thousand men by appealing to their prejudices quicker than you can convince one man by logic.”

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    JD [OP]
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    So basicly a 4 MOA dot will cover 4" of a target at 100 yards...

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    Correct

    Sorry the Wikipedia article was not that good.

    http://mywebpages.comcast.net/rob.no...ot_sights.html

    This should be a little better.
    “You can sway a thousand men by appealing to their prejudices quicker than you can convince one man by logic.”

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    JD [OP]
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    Well I don't plan on trying to shoot past 200 yards ever again. If I do it won't be with a 16" bbl, so I think 8" at 200 yards will do for the SOCOM, eventually I'd like to get a rear mount and an ACOG but that's a little pricey...

    Then again there's also this: http://www.aimpoint.com/products/aim...aimpoint_3xmag


    Thanks PGrass, the 2nd article was much more helpful, that's what I thought the MOA breakdown was but for the life of me I couldn't remember.

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    Your welcome,

    That Aim Point is nice and I have thought about them but I just can't justify me spending the money on the yet. I've got more guns to buy first.

    I have thought about putting my Red Dot on my M-1 carbine if I could find a good mount.

    I wouldn't shoot it over 150 yards anyway and if I did I would expect the rounds to be in a 12" group well maybe 8 " from a bench
    “You can sway a thousand men by appealing to their prejudices quicker than you can convince one man by logic.”

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    JD [OP]
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    Quote Originally Posted by pgrass101 View Post
    Your welcome,

    That Aim Point is nice and I have thought about them but I just can't justify me spending the money on the yet. I've got more guns to buy first.
    I'm selling the quad rail from my SOCOM II on Eaby and that will be financing my Aimpoint.

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    Minute-Of-Angle

    The term "minute-of-angle" (MOA) is used regularly by target shooters at the range, but is probably understood, thoroughly, by few (the same goes for mil-dots). Defined loosely, one MOA = 1" @ 100 yards; so, if you shot your rifle 5 times into a 100-yard target and every shot went into a one-inch circle you had drawn on the paper, then your rifle could be said to shoot 1 MOA. Likewise, if every shot goes into a two-inch circle at 200 yards, then you're shooting 1 MOA. A 10-inch group at 500 yards would be 2 MOA.

    Now for the fun part. There are 360 degrees in a circle. Each degree can be broken down further into minutes. There are 60 minutes in a degree. Likewise, there are 60 seconds in a minute. Now, to figure out the distance subtended by 1 minute at any particular distance, we need merely to plug those two values into a simple trigonometric equation. The tangent function fits the bill nicely. Here's the equation:
    tan(angle) = distance subtended/distance to the target (units must be consistent--e.g., 1/36 of a yard [1"] divided by 100 yards)

    Now, we know the angle (1 minute or 1/60 of a degree) and we know the distance to the target (100 yards), but we need to figure out the actual distance subtended at the target (i.e., is 1 MOA actually 1" @ 100 yards?). What we need to do is solve for "distance subtended." Here's our final equation:
    tan(angle)*distance to the target = distance subtended

    Make sure your calculator is in "degree" mode (as opposed to "radian" or "gradian") and type in 1/60 (for degrees) and hit the "tangent" button. Then multiply that by 100 yards. This should give you the distance (in yards) subtended at 100 yards. Multiply this by 36 to get inches. The answer should be:
    1.047197580733"

    This is just a hair over the commonly quoted "one inch." At 1000 yards, this would be almost 10 1/2 inches. Apparently, it is just a coincidence that 1 MOA happens to be REALLY close to 1" @ 100 yards. It is, however, quite convenient.

    The Mil-Dot

    The "Mil" in "Mil-Dot" does not stand for "Military"; it stands for "milliradian." The radian is a unitless measure which is equivalent, in use, to degrees. It tells you how far around a circle you have gone. 2 PI radians = 360 degrees. Using 3.14 as the value of PI, 6.28 radians take you all the way around a circle. Using a cartesian coordinate system, you can use "x"- and "y"-values to define any point on the plane. Radians are used in a coordinate system called "polar coordinates." A point on the plane is defined, in the polar coordinate system, using the radian and the radius. The radian defines the amount of rotation and the radius gives the distance from the origin (in a negative or positive direction).

    ANYWAY, the radian is another measurement of rotation (the degree/minute/second-system being the first). This is the system used in the mil-dot reticle. We use the same equation that we used before, but, instead of your calculator being in "degree" mode, switch it to "radian" mode. One milliradian = 1/1000 (.001) radians. So, type .001 into your calculator and hit the "tangent" button. Then multiply this by "distance to the target." Finally, multiply this by 36 to get inches subtended at the given distance. With the calculator in "radian" mode, type:
    tangent(.001)*100*36 = 3.6000012"

    So, one milliradian is just over 3.6 inches at 100 yards. If we extrapolate, two milliradians equal about 6 feet at one-thousand yards. You'll see the importance of this, shortly.

    The Mil-Dot Reticle

    The mil-dot reticle was designed around the measurement unit of the milliradian. The dots, themselves, were designed with this in mind and the spacing of the dots was also based upon the milliradian. This allows the shooter to calculate the distance to an object of known height or width. Height of the target in yards divided by the height of the target in milliradians multiplied by 1000 equals the distance to the target in yards. For example, take a 6-foot-tall man (2 yards). Let's say that the top of his head lines up with one dot and his feet line up four dots down. So: (2/4)*1000 = 500 yards away. This same tecnique can be used to estimate lead on a moving target or to compensate for deflection on a windy day.

    The distance from the center of one dot to the center of the next dot is 1 milliradian. We are told (by the folks at Leupold) that the length of a dot is 1/4 milliradian or 3/4 MOA (Given this much information, one can determine that the distance between dots is 3/4 milliradian.).* I use the term "length" because the mil-dot is not round. It is oblong. The "dots" on the verticle crosshair run oblong in the vertical direction. The dots on the horizontal crosshair run oblong in the horizontal direction (i.e., they are lying on their sides). The width of each dot is an arbitrary distance and is not used for any practical purpose. Like a duplex reticle, the mil-dot reticle is thicker towards the edges and uses thin lines in the middle where the dots are located and the crosshairs cross. The distance between the opposite thick portions is 10 milliradians.

    *NOTE: 1/4 milliradian = .9" and 3/4 MOA = .785", so, obviously, a mil-dot cannot be both 1/4 milliradian and 3/4 MOA. I called Premier Reticles (they make Leupold's mil-dot reticles) and got an explanation: the dots on their mil-dot reticles are 1/4 mil. They are not 3/4 MOA. Apparently, they (Leupold?) just figured that more shooters understand MOA than milliradians, so they just gave a figure (in MOA) that was close, but not super precise.

    Confused?
    1 Mil Increment
    100 yds - 3.6"
    200 yds - 7.2"
    300 yds -12"
    400 yds - 14.4"
    500 yds - 18"

    here are some easy places to look:
    http://www.shooterready.com/mildot.html
    http://www.eabco.com/Reports/MildotRep01.htm
    Last edited by goawayfarm; April 11th, 2007 at 04:03 PM.
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    Thumbs up You rule!

    Now that's a good post, this should be stickied on every boad where optics are discussed...

    Thanks GoAwayFarm, I'm going to copy and paste that and save it for further study and reference.

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    Get all fancy and scientific Goawayfarm

    Great post I'm saving it.
    “You can sway a thousand men by appealing to their prejudices quicker than you can convince one man by logic.”

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    Another alternative to regular red dot sights is the EOTech holosight. It's got a 1 MOA dot in the centerwith a 65 MOA ring around it. The dot much finer than most red dot sights, which is great for long range shooting, while the ring is large enough for very fast, coarse aiming at close range. It's a pretty good combo allowing both speed and accuracy. The downside is that EOTechs are pretty pricey compared with most red dots.

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    Quote Originally Posted by jdlv4_0 View Post
    Now that's a good post, this should be stickied on every boad where optics are discussed
    The definition works just as well with iron sighted rifles.

    The USGI windage and elevation knobs on the M1 and M14 rifles are all 1 MOA clicks.

    The USGI elevation on the M16A2's rear sight is a little over 1 MOA. Its windage is 1/2 MOA.

    The National Match sight on an AR-15 service rifle has 1/4 MOA clicks. Here's mine:


    Other target rifles, such as this match rifle for NRA Highpower also have 1/4 MOA sights, but they are even more precise (better made) than those on service rifles used in Highpower. Again, one of mine:

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    Quote Originally Posted by goawayfarm View Post
    Minute-Of-Angle
    The Mil-Dot
    Great post! Many thanks.
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    I have a Aimpoint clone on my AR. Am considering an EOtech, for faster shooting and more accurate due to dot size.
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    I copied the thread and stickied it for those that would like to have it as a reference. The stickied thread is closed, this one can continue to be posted in.....
    Bumper
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