'MOA' Explained

[CountryGunsmith]

Magnus Ursus
Member
Posts: 10
(3/2/02 9:07:01 am)
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I'm shopping for a dot or scope, and frequently see the term "MOA" as in '4 MOA dot'.
What does this mean.

Also, when someone speaks of their ability to shoot sub MOA groups at 100 yards, what does that mean?

Thanks
Big Bear

Edited by: Magnus Ursus at: 3/2/02 9:08:22 am

Zigzag2
*TFF Senior Staff*
Posts: 2502
(3/2/02 9:16:50 am)
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The "Mil Dot" reticle is a sophisticated instrument for range finding and shot placement. 1 "Mil" is the distance between 2 dots and represents 1 yard at a distance of 1,000 yards
I hope this helps...


AntiqueDr
*TFF Senior Staff*
Posts: 2215
(3/2/02 9:58:06 am)
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ezSupporter
Re: MOA in scope language
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That means that the dot itself subtends 1"/100yd, 2"/200yd, etc. The coarser the dot, the coarser the sight picture. Most target scopes have dots in the fractions of MOA, while the 'Red-Dot' type sights have the 2MOA, 4MOA, etc.

Two separate applications.

We Buy Guns! 1 - 100, Antique or Modern!
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LIKTOSHOOT
*TFF Senior Staff*
Posts: 4013
(3/2/02 10:13:28 am)
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Hey, a subject I know a little about.

MOA>>>

MOA`s

1" @ 100 yards

2" @ 200 yards

3" @ 300 yards


ect....ect....ect.

Sub MOA`s would be less than standard.....

1/2" @ 100 yards, this would be sub MOA. LTS

gun runner john
*TFF Staff*
Posts: 479
(3/3/02 12:39:31 pm)
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Actually, MOA means Minute Of Angle, and at 100 yards, I believe this is 1.0472 inches. Most folks round that to 1 inch at 100 yards. Here's all you ever wanted to know about MOA.

Calculating Minute of Angle

The angle of an arc is expressed in number of degrees. There are 360 degrees of arc to a full circle. Each degree consists of 60 minutes of arc. The distance covered by the measure of arc is relative to the circumference (total distance around the circle) it is contained within. Knowing the radius (distance to center of circle) circumference is easily calculated by using the constant pi . The ratio (represented by pi ) of circumference is constant to diameter (radius x 2) regardless of circle size. The precise value of pi is so far unknown to man but is normally resolved to 3.1416 or 3.141 for our purposes.


Suppose a circle with a 6 inch radius. Circumference can be calculated as:

circumference = (radius x 2) x pi
circumference = (6 x 2) x 3.1416
circumference = 12 x 3.1416
circumference = 37.6992 inches

The distance covered by 1 degree of angle (37.6992 / 360 or, circumference divided by 360 degrees) is 0.1047 inch at 6 inches from center of circle.
And, 1 minute of angle represents (0.1047 / 60 or, 1 degree divided by 60 minutes) 0.001745 inch at 6 inches from center of circle.

Knowing what MOA represents allows us to calculate its value to any distance.
Six inches (the radius of the above example) is 1/600th of 100 yards: (100 yards x 36 inches) / 6 inches = 600
Therefore, the value of MOA at 100 yards is 1.047 inches (0.001745 x 600 = 1.047)
At 50 yards 1/2 the 100 yard value; 70% @ 70 yards; twice @ 200 yards; 6 times @ 600 yards; and so on.
So, the difference between thinking in inches as opposed to MOA is 0.47 inch @ 1000 yards.