Definition of MOA

This is a discussion on Definition of MOA within the SOP forums, part of the Sniping Related category; I've been corresponding with a member on what the definition of MOA is. He's asking great questions which demand good answers. I've actually had to ...

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  1. #1
    Senior Member oneeyedmac's Avatar
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    Definition of MOA

    I've been corresponding with a member on what the definition of MOA is. He's asking great questions which demand good answers. I've actually had to go to the dictionary.

    Here is how Wikipedia define Minute of Angle, also known as an arcminute, as it relates to marksmanship:

    Firearms
    The arcminute is commonly found in the firearms industry and literature, particularly that concerning the accuracy of rifles, though the industry tends to refer to it as minute of angle. It is popular because 1 MOA subtends approximately one inch at 100 yards, a traditional distance on target ranges. A shooter can easily readjust his rifle scope by measuring the distance in inches the bullet hole is from the desired impact point, and adjusting the scope that many MOA in the same direction. Most target scopes designed for long distances are adjustable in quarter (¼) or eighth (⅛) MOA "clicks". One eighth MOA is equal to approximately an eighth of an inch at 100 yards or one inch at 800 yards.

    Calculating the physical equivalent group size equal to one minute of arc can be done using the equation: equivalent group size = tan(MOA/60) × distance. In the example previously given and substituting 3600 inches for 100 yards, tan(1 MOA/60) ∙ 3600 inches = 1.0471975511966 inches.

    In metric units 1 MOA at 100 meters = 2.90888208665722 centimeters.

    Sometimes, a firearm's accuracy will be measured in MOA. This simply means that under ideal conditions, the gun with certain ammunition is capable of producing a group of shots whose center points (center-to-center) fit into a circle, the average diameter of circles in several groups can be subtended by that amount of arc. (E.g.: a "1 MOA rifle" should be capable, under ideal conditions, of shooting an average 1-inch groups at 100 yards, a "2 MOA rifle" a average 2-inch groups at 100 yards, etc.) Some manufacturers such as Weatherby and Cooper offer actual guarantees of real-world MOA performance.

    Rifle manufacturers and gun magazines often refer to this capability as "Sub-MOA", meaning it shoots under 1 MOA. This is typically a single group of 3 to 5 shots at 100 yards, or the average of several groups. If larger samples are taken, i.e. more shots per group, then group size typically increases


    So if you are zeroing your rifle and your scope has 1/4 MOA clicks and you find that you shoot 2" low at 100 yards you need aproximately 8 clicks to get to zero. If it's 2" low at 200 yards you need 16 clicks.

    Clear as mud right?

    Can we sticky this as it's a question that comes up fairly regularly?

  2. #2
    Senior Member boone's Avatar
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    Howdy

    Good information.
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    SOLD PENDING FUNDS!

  3. #3
    Senior Member RayaK9's Avatar
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    Re: Definition of MOA

    Quote Originally Posted by oneeyedmac

    So if you are zeroing your rifle and your scope has 1/4 MOA clicks and you find that you shoot 2" low at 100 yards you need aproximately 8 clicks to get to zero. If it's 2" low at 200 yards you only need 4 clicks.

    Clear as mud right?
    :? ummmmmmmmmm noooooooooo. If I was 2" low at 200 why isn't it 16 clicks up? See this is where I need understanding. Come-ups/downs and the inbetween clicks! I know how to do the math and use my mil-dot to measure range, but adjusting up/down is more than a little fuzzy! And I am not even touching windage yet. But I have a question regarding ranging......can a scope be used to measure a distance of LESS than 100 yards?
    Remington 700 VTR .308

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    *I love my VTR, couldn't ask more from a hunting rifle*

  4. #4
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    That is why thinking in clicks gets people confused. Think in MOA. 1 MOA is approx 2" at 200 yards so if you were 2" low then you need 1 MOA of elevation so you dial on 1 MOA on your scope elevation knob. That's why the big numbers are there. No need to count clicks. Just dial to the 1. It doesn't matter if your scope adjusts in 1/8, 1/4. 1/2 or full MOA. Just dial to the 1 MOA mark. If you were 2" low at 100 yards then you need 2 MOA as 1 MOA at 100 yards is approx 1". So you dial to the big number 2 on the elevation knob.

    Also windage is no different. Just left and right instead of up and down.

    A scope can be used to measure a target at any range as long as you know the target size and can get an accurate mil or MOA reading.

  5. #5
    Senior Member oneeyedmac's Avatar
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    Re: Definition of MOA

    Quote Originally Posted by RayaK9
    Quote Originally Posted by oneeyedmac

    So if you are zeroing your rifle and your scope has 1/4 MOA clicks and you find that you shoot 2" low at 100 yards you need aproximately 8 clicks to get to zero. If it's 2" low at 200 yards you only need 4 clicks.

    Clear as mud right?
    :? ummmmmmmmmm noooooooooo. If I was 2" low at 200 why isn't it 16 clicks up??
    You're right, thanks for the correction.

    Rob is very experienced, probably one of the mroe experienced shooters out there, and any one of us would be wise to take his counsel.

  6. #6
    Senior Member RayaK9's Avatar
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    ahhhhhhhhhhhhhhhhhhhhhhhhh, ok....that makes a little more sense.........
    Remington 700 VTR .308

    Millett TRS-1

    Harris and Karsten enhancments
    *I love my VTR, couldn't ask more from a hunting rifle*

  7. #7
    Senior Member becks's Avatar
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    Great to see that you posted this, I hope it helps people cleer up somethings like it did for me.
    Great post!
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  8. #8
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    Am I right in thinking, measuring group size, you measure from the outside of one hole, to the inside of another hole ? Do you measure the holes that are farthest apart in a three shot group ?
    Thanks

  9. #9
    Senior Member becks's Avatar
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    You measure from the middle of the outside hole to the middle of the other outside hole, that is...unless you only have one hole :wink:
    #2 Infidel
    Jeff Dorr...Gone but not forgotten

    Next builds:
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  10. #10
    Senior Member oneeyedmac's Avatar
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    Quote Originally Posted by Doc One Shot
    Am I right in thinking, measuring group size, you measure from the outside of one hole, to the inside of another hole ? Do you measure the holes that are farthest apart in a three shot group ?
    Thanks
    You can measure from the center to the center of the two holes that are farthest apart. Sometimes it's difficult to determine where the center of a hole is if you have one ragged hole. So measure from the outside to the outside of the holes farthest apart and subtract the caliber of the projectile.

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