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Old August 31, 2014, 08:20 AM   #1
NHSHOOTER
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MOA

Dont know if this is the right place for this question but, here goes. When we speak of MOA, I know that MOA is approx. 1" at 100 yds. My question is, is 1MOA approx 2" @ 200, 3"@ 300 and so on? I have heard shooters say that they shoot 1 MOA @ 600 yds. do they mean that the bullets are hitting no more than 6" at the widest point?
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Old August 31, 2014, 08:32 AM   #2
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Yes, exactly.
MOA is an angle so as the length expands so does the width.
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Old August 31, 2014, 08:41 AM   #3
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Before someone else says it, a MOA is actually 1.047" per hundred yards but for all practical purposes, yes, a MOA at 600 yards would be 6 inches. (6.282").

We speak of MOA as 1 inch because, it all reality, who can tell the difference of 1/4 inch (0.282) at 600 yards?

A 1 MPH FV wind will move a bullet (30 cal 175 SMK w/MV 2600 fps) .5 MOA at 600 yards, basically 3 inches.

I've never seen a true "no wind" day.

Don't get hung up on MOA.
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Old August 31, 2014, 12:41 PM   #4
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"MOA" is an acronym for "Minute of Angle" or "Minute of Arc."

Conveniently, 1 minute of angle happens to cover a range of approximately one inch at a distance of 100 yards. Thus, at 100 yards, 1 MOA = 1-inch groups. It's a straight geometric relationship, so 1 MOA is also 2 inches at 200 yards, 3 inches at 300 yards ... and 6 inches at 600 yards.

But that's theoretical. In actual shooting, a bullet takes six times as long to fly 600 yards (generalization) as it does to fly 100 yards. That's six times as much time for wind and gravity to affect the line of flight. Even though mechanically 1 MOA at 100 yards is exactly the same as 1 MOA at 600 yards, in real life you may be able to hold a 1-inch group at 100 yards but not hold a 6-inch group at 600 yards.
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Old September 2, 2014, 09:42 AM   #5
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Quote:
"MOA" is an acronym for "Minute of Angle" or "Minute of Arc."
To explain it one step further, we commonly measure angles in degrees. A circle has 360 degrees of angle. When talking about very small angles, a degree is much too large, so a degree is divided into 60 minutes. That is, 60 MOA + 1 degree. Minuted of angle can be further subdivided into "seconds of angle."

1 degree = 60 minute of angle = 360 seconds of angle
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Old September 2, 2014, 11:11 AM   #6
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and to take it a step further again

...,the circumference of a circle is π * D (pi times the diameter); and there are 360 degrees * 60 minutes per degree = 21600 minutes in one circumference.

At 100 yards, the radius is 100 * 3 * 12 inches so the diameter is twice that. Tat is, the circumference is π * 200 * 3 * 12 = 7200 * π inches.

Setting the two circumferences equal:

360 * 60 minutes = π * 200 * 3 * 12 inches

1 minute = π / 3 inches

π is roughly 3.1459 and it goes on, a repeating decimal... but π/3 is about 1.04 or almost 1.05 inches at 100 yards, and scales linearly with distance (radius, diameter, range to target, whatever the name.).
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Old September 2, 2014, 02:22 PM   #7
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Quote:
Originally Posted by Armorer-at-Law
1 degree = 60 minute of angle = 360 seconds of angle
You're missing an extra zero there.

Quote:
Originally Posted by BobCat45
π is roughly 3.1459 ...
And you are missing a one.
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Old September 2, 2014, 03:15 PM   #8
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Eeek! You're right!

...that's why I use the word "roughly" so often - I'm wrong a lot of the time.

3.14159 - 3.1459 = -0.00431 or roughly 0.137% low.

Sorry.
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Old September 2, 2014, 07:47 PM   #9
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Not wanting to pile on, but . . . pi is not a repeating decimal. Repeating decimals are rational numbers, i.e., numbers that can be expressed as a fraction (ratio) of integers. Pi is an irrational number, and therefore does not repeat when expressed in decimal notation.
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Old September 2, 2014, 07:52 PM   #10
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Ok, I think the original question has been answered.
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