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Could someone give me an educated explanation as to what this means? MOA and sub MOA.
A circle is divided into 360 degrees.
Each degree is divided into 60 minutes.
If you pretend you are at the centerpoint of a circle and the target is on the circumference of the same circle then you can measure your accuracy in minutes of angle.
So, let's say you are 100 yards away from your target.
That makes the radius of the imaginary circle 100 yards. We can calculate the total circumference of the circle using 2 x pi x radius.
The total circumference of the circle is then 628.32 yards. Divide the circumference by 360 to get the distance on the circle defined by a single degree.
One degree of angle on a 100 yard radius circle is therefore 1.745 yards.
Now, divide that by 60 to get the distance on the circle defined by a single minute.
When we do that we find that one minute of angle on a 100 yard radius circle is 0.029 yards or 0.087 feet or 1.047 inches. That's pretty close to one inch and most folks just call 1 MOA and 1 inch the same thing at 100 yards.
You can calculate what 1MOA is at any distance using the following formula.
1MOA (inches) = distance (yards) / 95.49
At 50 yards, 1 MOA is 0.52 inches
At 75 yards, 1 MOA is 0.79 inches
At 150 yards, 1 MOA is 1.57 inches
At 250 yards, 1 MOA is 2.62 inches
Note that most people approximate these numbers by rounding them DOWN to the nearest quarter inch in practice. That makes it easy to calculate--simply divide the yardage number by 100 to get the APPROXIMATE value of 1 MOA in inches.
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This should really be reduced to:Note that most people approximate these numbers by rounding them DOWN to the nearest quarter inch in practice. That makes it easy to calculate--simply divide the yardage number by 100 to get the APPROXIMATE value of 1 MOA in inches.
Does the gravitational constant enter into that by any chance? If so, the equality statement should be changed to "450240 becomes 450436". (I won't vouch for the exactness of the statement; I'll take your word for it. )JohnKSa said:Yes--and if you're holding a firearm, then 450240=450436.
I thought it was 450437. No wonder my power factors were off.JohnKSa said:Yes--and if you're holding a firearm, then 450240=450436.
That's me, to a 'T'. Arcane factoids are such fun!But it's interesting to some folks to know the origins of terms and the exact values instead of the practical approximations.
I would think that to use a tangent relationship, the middle of the group should be used, not one edge or the other. So it would be- 2 times the arctan of one half the groupsize over the distance to target.Arcane factoids are such fun!
Windage and elevation are solved using trigometric functions all the time in precision long range shooting.I've never seen or heard of anyone performing trigonometric calculations on the range.
My understanding is that the 450240 was a typo that "became fact" before anyone figured it out.Does the gravitational constant enter into that by any chance? If so, the equality statement should be changed to "450240 becomes 450436".
Infidel,The two numbers at 100 yards are 1.047197551 and 1.047197581, a significant difference of 0.000000030 inches (at 100 yards).
Yes! I have tried explaining the idea of twice the tan of half the angle, and I usually get blank stares and get sent to fetch the next round. Thank you. Then there's using the sin, measuring to the head instead of to the feet, or measuring to the belt buckle and using twice the sin of half the angle. Or, maybe average all of the above? (Uhhhh ... arctan is an angle. That is, arctan 1.04719/3600 = 1/60 degree (= 1 minute) (more or less)).Bwana John said:I would think that to use a tangent relationship, the middle of the group should be used, not one edge or the other. So it would be- 2 times the arctan of one half the groupsize over the distance to target.
Wow. I never thought of that. I so like learning things. Thank you. Now, I gotta make a curved template for my targets....JonKSa said:I always put a slight curve in my target paper to account for that.
arctan 1.04719/3600 = 1/60 degree (= 1 minute) (more or less)).