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Old October 15, 2007, 08:34 PM   #1
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What is the MOA and how does it affect long distance shots?

Okay, so what is MOA? I know it is something about shooting 1" groups or under at 100 yards, right? How do I calculate it? If I shoot sub-MOA at 100, what can expect at 500 with practice? How do I use that to compensate for how far down my bullet will be at different ranges? How can I use it to better my shooting for long ranges?

I know, those are a lot of questions. But, I sit in class all day and wonder about these things. God I love college, at least it provides me with something to do for the few hours a day...

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Old October 15, 2007, 08:53 PM   #2
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I can help a bit, MOA = Minute of Angle
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Old October 15, 2007, 08:59 PM   #3
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think of MOA as how much you can expect the bullet to deviate in the shape of a cone.

if a rifle shoots 1 moa, it means that at 100 meters all shots should fall in one inch.

this also means that at 500 meters you can expect a grouping of 5 inches, this is still 1 moa.
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Old October 15, 2007, 09:35 PM   #4
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MOA= Minute of angle. 1/60th of a degree of angle. 1.04719756"@ 100yds. Will a rifle that shoots under the MOA @ 100yds do 5" groups @500? Maybe, but for certain not guaranteed. Too many variables to predict there, without more info.

To use MOA to compensate for drop at distance, you need to know a few things:
1. What is the predicted drop for your bullet at the speed you're launching it.
2. How many clicks does your scope or other sight need to move a minute (does it have 1/4 min clicks, 1/8th min, something else?)
3. The range to your target.

As an example: I just shot my first 600yd prone match with iron sights on an AR. I worked up a load pretty quickly, only had time to chronograph it at 100yds. So I ran the velocity and bullet info in a ballistics program to get a predicted come-up for the match. The program called for 12.8 MOA of correction so I went up 15 MOA with the front sight, and down 2 MOA (8 clicks) with the rear. I was pleased to no end to see the target go down and to find that I only had a small correction to make to get spot on, elevation-wise.

Hope that helps

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Old October 15, 2007, 10:20 PM   #5
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Most folks take the distance to the target in yards and divide by 100 and call that 1 MOA in inches.

exercion is correct, however, the true value of 1MOA is actually a bit larger than that. If you want to get closer to the true value, divide the yardage to the target by 95.5 to get the approximate value of 1 MOA in inches.

If you want to get the exact value, calculate the circumference of the circle that has a radius that is the length from the shooter to the target. Divide the circumference of the circle by 21,600 (360 degrees x 60 minutes) to get the value of 1 MOA for that particular range. There are 360 degrees of angle in a circle and 60 minutes of angle (MOA) in a single degree. That means there are 21,600 minutes of angle (MOA) in a complete circle.

So at 100 yards the MOA would be

2 x pi x 100

which would be about 0.0291 yards or 1.047 inches (rounded to 3 decimal places).

If we had used the approximation above, we would have calculated:


which would also have given us 1.047 inches (again rounded to 3 decimal places).

Ok, about now you're wondering why anyone uses MOA. We just did all these calculations to get inches from MOA, why not just mark sights and scopes in inches?

Because if you did that, the adjustments would only be correct for one particular range. If they're marked in MOA, they're correct for any range as long as you know how what an MOA is.
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Old October 16, 2007, 12:40 AM   #6
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Good to see most of the MOA poo got covered so I don't need to type a novel. Another aspect is determining if your rifle and ammo shoots MOA.

Minimum is 3 shot group though I feel it really doesn't tell you anything, 5 shot groups are better, but a 10 shot group is really a good indication of what your doing.

So at 100 yards in perfect conditions shoot your rifle off a rest. Slow fire your group and measure the distance from edge to edge of the two farthest hits. Then subtract the diameter of your bullet. This is what your rifle and ammo are doing. What everyone is looking for is 1 moa or moa. If your doing sub moa then that is a exceptional rifle ammo combo. You read and hear about A LOT more sub moa rifles than you actually see at the range. Funny how that is
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Old October 16, 2007, 04:59 PM   #8
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It's not exactly right, but for practical purposes a MoA an inch at 100 yds.
The important stuff has more-or-less been covered. Here's just a little of how it helps:
-If you start keeping notes on the ambient conditions, you can start to figure out the correct settings for any condition. You start thinking in terms of "minutes" instead of "inches". As you learn to dope wind and range, you can guesstimate a very accurate setting.
-Your scope is generally calibrated in MOA, for example 1/4 MoA per click. It makes it easier to rapidly dial in a setting for a given range.
-You should strive to attain the ability to shoot to the capability of your equipment, and not get disheartened if you can't exceed it. I've seen many instances where someone was unhappy with his groups, yet a little quick math revealed that he was already doing about as well as he was going to and his goal was unrealistic.
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