Posted: 3/7/2001 5:47:11 PM EST
I should really know this but i dont.
Thanks
brian73



Refers to a very small portion of a circle. The term is usually considered to mean that a rifle shooting subMOA, ie Minute of Angle..means that it shoots groups of UNDER 1" at 100 yds, from a rest. Anybody else got a more technically correct definition? That's the best I can do..and I can't even see that well...LOL



You're right. I'll add that MOA is defined as 1/60th of a degree, hence the name "minute". Just imagine a tringle with two sides 100yds long and the third side 1" long. The angle between the two long sides is about 1 MOA.



thanks guys, I had a hunch it was around a 1" group, but just couldn't figure out what MOA stood for.
brian73



As Fred said, MOA is Minute Of Angle. A minute is 1/60th of a degree. The practical application of this with reference to shooting is that one minute is almost exactly one inch at 100 yards (or 3600 inches). If I'm thinking clearly and my math is right, sin(1/60 degree)*3600 inches = 1.047... inches.



Yeah, it's an astonomical or navigational term, minute, that is. When you extend your arm your fist covers about 10 degrees (useful for spotting stars, ie. star xyz is 15 degrees below the north star, fist and a 1/2 below). Each degree is divided into 60 minutes.
So, if you hold our your fist out at the shooting range and divide by knuckles and thumb (1/5th each), you will see that each knuckle covers about 2 degrees or 120 minutes. That's about 10 feet at 100 yards...



BTW, astronomers commonly use "seconds of angle" which are 1/60 of a MOA, reffered to as "arcseconds". They call MOA "arcminutes".



Any weapon producing less than 1 MOA @ 100 yards would be considered a sniper rifle by Marine Corps standards: "The unique characteristics of the M40A1 Sniper Rifle are: commercial competitiongrade heavy barrel, McMillan fiberglass stock and butt pad, modified Winchester Model 70 floorplate and trigger guard, and modified and lightened trigger. In addition, each stock is epoxy bedded for accuracy and all weapons must shoot less than one minute of angle (MOA)." [sniper]


<font size=2>The Strong Take From The Weak....The Smart Take From The Strong</font id=s2>

Originally Posted By qwijibo:
As Fred said, MOA is Minute Of Angle. A minute is 1/60th of a degree. The practical application of this with reference to shooting is that one minute is almost exactly one inch at 100 yards (or 3600 inches). If I'm thinking clearly and my math is right, sin(1/60 degree)*3600 inches = 1.047... inches. View Quote 


David M  Qwijibo is right. Your error is the circumference is 2*pi*r not pi*r. So 1 MOA is 1.047 inches @ 100yds. But your conclusion is correct, since .523 radius group=1.047 diameter group.



WHAT?? Well ##$%$##$#^#^^#^#$%!!!!! [:(!]
You are of course, both right. Circumferance=Diameter x pi. Thank you, MadMatt. My apologies Qwijibo.



MOA doesn't have anything to do with yards (or 100 yards), it's a Metric measurement. It happens to end up being just over an inch at 100 yards by coincidence. There's also no such thing as 1 MOA at 100 yards, like the expression "Knots pew hour." Even if it was based on yards, a MOA is a unit of angle measurement in itself, it doesn't have anything to do with a measured distance. A hard mounted GAW, even a good 50 BMG can manage 1MOA at one mile...... but it (the imaginary cone) sure the hell isn't one inch anymore, it's over 58".
FWIW, one "SECOND of angle" is the size of a dime  [u]at 4.6 miles! [/u]
[url]http://www.google.com/search?q=cache:www.metricusa.com/METINFO4.HTM+WHAT[/url]
Table 7  Units in Use With the International System
Name Symbol Value in SI unit
degree (angle) Â° 1Â°= (/180) rad
minute (angle) Â´ 1Â´= (1/60)Â° = (?/10 800) rad
second (angle) Â´Â´ 1Â´Â´ = (1/60)Â´ = (? /648 000) rad


Perfection! Wait ... what? Wadaya mean "generation 1,.. 2,.. 3,.. and 4"?

Far be it for me to take a hard line position on this thread. But Metric? I thought all metric was based on numbers of 10. Degrees and such were thought up long ago by the Greeks, or so I thought. Way before metrics.
I sure do agree, MOA is relative to the distance of the shot. The angle widens proportionately.



Just as I thought. I'm not gloating though. You can bet on that!
Accepted Units.
For practical reasons a number of nonmetric units are accepted for use. These include units
of time (minute, hour, etc.), units of plane angle (degree, etc.), and a few units for special a few units for special applications, such as the nautical mile, used in navigation. Section 5 includes accepted units and shows their areas of application. These units may be used in full compliance with the provisions of the amended Metric Conversion Act, EO 12770, and the Federal Register Notice, "Metric System of Measurement; Interpretation of the International
System of Units for the United States" (55 F.R. 52242, Dec. 20, 1990).



Correct, MOA doesn't have anything to do with yards, or I might add, the metric system. To phrase it precisely, a 1" circle subtends an angle of 1 MOA at 100yds. But at the shootin' range 1 MOA = 1" @ 100yds. = 2" @ 200yds. etc.



David (quit gloating =), you're right. It's not metric (or Olm), I don't know WTH it is.
I love topics like this though......
Did you ever hear what the metric system (linear measurements  I mean) is based on?
What exactly IS a meter?


Perfection! Wait ... what? Wadaya mean "generation 1,.. 2,.. 3,.. and 4"?

C'mon, don't look it up (I just found out a few months ago).


Perfection! Wait ... what? Wadaya mean "generation 1,.. 2,.. 3,.. and 4"?

The distance from the North Pole to the equator, 10,000,000 meters. Now, I'm gloating![8D]
Or, is it 1,000,000 meters? Now, I've done forgot! No longer gloating.



"To phrase it precisely, a 1" circle subtends an angle of 1 [u]MOA at 100yds.[/u]"???
MM, it's also 1MOA at 1, 10, 25, 50, & 300 yards too.


Perfection! Wait ... what? Wadaya mean "generation 1,.. 2,.. 3,.. and 4"?

Yeah, North Pole to the equator (through Paris) is 10,000,000 meters....


Perfection! Wait ... what? Wadaya mean "generation 1,.. 2,.. 3,.. and 4"?

The meter was originally defined as one ten millionth of the distance between the north pole and the equator, along the meridian through Paris. No wonder Americans hate the metric system.



Originally Posted By WILSON:
"To phrase it precisely, a 1" circle subtends an angle of 1 [u]MOA at 100yds.[/u]"???
MM, it's also 1MOA at 1, 10, 25, 50, & 300 yards too. View Quote 


You asked a question and you got a answer. and a half. Thanks guys we all needed brushing up on MOA 101.



Originally Posted By WILSON:
"To phrase it precisely, a 1" circle subtends an angle of 1 [u]MOA at 100yds.[/u]"???
MM, it's also 1MOA at 1, 10, 25, 50, & 300 yards too. View Quote 


Sorry for posting the whole thing guys. Maybe this will settle the dispute.
XII. Accuracy
C. Miscellaneous
4. What is a Minute of Angle (MOA)?
by Robert W. Current (rob@current.nu) and Trevor M. Riedemann (tmr@iastate.edu) .
It is a measurement of angle, a subdivision of a degree. There are 360 degrees in a full circle
4 quadrants = 1 circle
90 degrees = 1 quadrant
60 minutes = 1 degree
60 seconds = 1 minute
21,600 minutes = 1 circle
So they are all just measurements of an angle, should be listed in any fact finder or such.
The reason it is so widely used in the shooting sports is because if you measure an angle of one minute the lines almost run parallel at short distances, but at long distances you can see them separate. And quite conveniently they separate to 1 inch apart when you get 100 yards from the point they cross. That works out great for measuring rifle accuracy (in an idealized situation, no wind, ...):
Shots spread at an angle, increasing group size as distance from the target increases.
Diagram 1
"M" is the muzzle and "d" is the distance to the target, now it is easy to see the closer you are to the Target, the more likely you are to hit it (we all know that, at least intuitively) and it can be seen it is some function of an angle. That is why accuracy is ideally measured in angles not just shot spread.
So, if you have a 1 Minute of Angle (1 MOA) rifle, you can expect about one inch groups at 100 yards, 2 inch groups at 200 yards, 3 inch groups at 300 yards.
To explain this if full detail requires the use of trigonometry/geometry:
Diagram 2
At a distance of 100 yards from the target, length "d" on the diagram, you shoot a group that measures one inch, segment "C" on the diagram.
Then:
tan(q/2) = C/2d
(look at the addendum below to see how this is found)
Solving for theta
q = 2 tan1(C/2d)
For C = 1 inch
d = 100 yards = 3600 inches
q = 0.0159155 degrees = 0.9549 arcmin
Alternatively this can be made by an approximation:
S = Rq
where q is in radians solve for theta
q = S/R
S is approximately equal to C (1.0000004" ~ 1")
R is approximately equal to d (100.000001 yards ~ 100 yards)
q = C/d = 1 inch/3600 inch = 0.00027777 radians = 0.9549 arcmin
So, your one inch group at 100 yards is really 0.95 MOA group!
Want to go into more detail? Well a degree is symbolized by a little o above and to the right of the number, a minute is symbolized by a single apostrophe (') and a second is abbreviated with a double apostrophe ("). You know what that means? I could say I shot a 1' group (a "one minute" group), and it could mean I shot a group that was 0.95 inches at 100 yards, or even a 1.8 inch group at 200 yards. This use of the symbols is really one of my pet peeves, that I never really rant about, I just let people sound silly and laugh to myself later. I shot a 1" group. Wow, did I read that article right, he said 1" that is one second right? It has to be, he didn't say 1 inch at a 100 yard distance, he didn't even mention distance, so he must be reporting accuracy in MOA, and that would work out to be 1/60 (one sixtieth) of an inch at 100 yards. Man those guys are so good, I must really suck, I will never be able to shoot that well.
But, even this all seems to be an ideal way of measuring things for shooting, you have to keep in mind that the real world is rarely ideal. You really have to take a few more things into a



"Maybe this will settle the dispute."
I don't think there's any dispute. We're all on the same page, just bored, & playing with words.


Perfection! Wait ... what? Wadaya mean "generation 1,.. 2,.. 3,.. and 4"?

I think I'll just settle for "right between the eyes" at 100 yards.


My opinion is more important than your opinion. But that's just my opinion.
I had to throw all my guns overboard to keep from getting arrested when I sailed into Mexico. 
Thats way to complicated for me. Hows your ar shoot...1" groups...Great! Thats all i need to know. My head is so full of useless information that if i tried to remeber all those formulas i would have to forget something. Like my wifes name..



hd man, be sure to qualify that with a range. 1" at 100yd is good. 1" at 5yd is horrible. =)



Wilson,
And ya'all are doing a mighty fine job of it!
Thanks for the math lesson.


Warm winds blowing, heatin' blue sky, and a road that goes on forever. I'm glad I'm in Texas!!
Paul Nester 
Originally Posted By WILSON:
"Maybe this will settle the dispute."
I don't think there's any dispute. We're all on the same page, just bored, & playing with words.
View Quote 


Now I know why the term (More information than I needed to know)is used.



hmmm.....i guess here in the Louisiana swamps we are a little backwards.....I thought MOA = Middle Of Arshole....hehehe. sorry couldn't resist it...hehee


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