I'm looking for a technical definition of MOA
- Thread starter Correia
- Start date
WalterGAII
Moderator
Am I nuts, or have you already initiated a thread like this before and had this explained to you in pretty good detail?
Steve Smith
New member
Rather than me typing an hour, go to this sight and read the page...the explanation of MOA is near the bottom.
http://www.swfa.com/mildot/index.html
http://www.swfa.com/mildot/index.html
Hi, Correia,
The question has been asked and answered before, but here it is in brief. A circle has 360 degrees, each of which is divided into 60 minutes and each minute into 60 seconds. Think of the protractor you had in grade school, with the little degree markings. If a rifle shooter is thought of as being at the center of the circle, the size of his group can be described in minutes of angle (MOA) or how big an arc the shots cover. By conicidence, one minute of angle equals about 1 inch at 100 yards, 2 inches at 200 yards, and so on.
So a rifle (and shooter) capable of placing a group of shots within a 1" circle at 100 yards is "shooting one minute of angle". Conventionally, groups are five shot unless otherwise specified, and group size is measured center to center of the farthest apart bullet holes. (If a center to center measurement is not feasible, the distance from the outside edges of the farthest apart holes can be measured, and the bullet diameter subtracted. This gives the same result.)
Jim
The question has been asked and answered before, but here it is in brief. A circle has 360 degrees, each of which is divided into 60 minutes and each minute into 60 seconds. Think of the protractor you had in grade school, with the little degree markings. If a rifle shooter is thought of as being at the center of the circle, the size of his group can be described in minutes of angle (MOA) or how big an arc the shots cover. By conicidence, one minute of angle equals about 1 inch at 100 yards, 2 inches at 200 yards, and so on.
So a rifle (and shooter) capable of placing a group of shots within a 1" circle at 100 yards is "shooting one minute of angle". Conventionally, groups are five shot unless otherwise specified, and group size is measured center to center of the farthest apart bullet holes. (If a center to center measurement is not feasible, the distance from the outside edges of the farthest apart holes can be measured, and the bullet diameter subtracted. This gives the same result.)
Jim
Destructo6
New member
Specifically, that would be a 1 inch radius circle at 100 yards.
See, since 100 yards equals 3600 inches and we're talking about a 1" radius circle at that range, we have an easy Trig problem: arcsin(1/3600) ~= .015915 degrees, which is sufficiently similar to one minute (1/60 degree) ~= .016667
Make sense now?
See, since 100 yards equals 3600 inches and we're talking about a 1" radius circle at that range, we have an easy Trig problem: arcsin(1/3600) ~= .015915 degrees, which is sufficiently similar to one minute (1/60 degree) ~= .016667
Make sense now?
WalterGAII
Moderator
Destructo sound so cool, but he be wrong wid his math.
Search Results for the string <MOA>, Match All, Any Date, All Forums, Subject Only. There's only eleven threads on this subject besides this one. Did you do a search, Larry?
Destructo6
New member
I'm not sure why arc length is being brought into this, seeing as the relation of arc length to radius is: arc length = radius * angle (in radians). Sure enough that the arc length of a sector with a 3600" radius and angle of one minute is .523599", but why would we be messing with an arc when we're measuring distance on a flat surface?
Aren't we talking of an angular deviation of the bullet impact to the point of aim? If so, then one minute at 100yds will give a circle with a ~1" radius.
Aren't we talking of an angular deviation of the bullet impact to the point of aim? If so, then one minute at 100yds will give a circle with a ~1" radius.
Ruben Nasser
New member
IT'S A 1" DIAMETER!!!!
Destructo, your math is right, but a MOA group is defined, as Jim Keenan put it: "...a group of shots within a 1"... Conventionally, groups are five shot unless otherwise specified,and group size is measured center to center of the farthest apart bullet holes."
So, we are not dealing with the deviation of the shots from the theoretical path (which, as you said,would lead to a 1" radius, and thus 2" grouping), but what we are doing is measuring the angle that subtends (covers) the entire group.
Then by definition, this arc (it's an arc, but due to the minute angle we can aproximate it to a line for the calculation you just did) it's the diameter of the group.
Destructo, your math is right, but a MOA group is defined, as Jim Keenan put it: "...a group of shots within a 1"... Conventionally, groups are five shot unless otherwise specified,and group size is measured center to center of the farthest apart bullet holes."
So, we are not dealing with the deviation of the shots from the theoretical path (which, as you said,would lead to a 1" radius, and thus 2" grouping), but what we are doing is measuring the angle that subtends (covers) the entire group.
Then by definition, this arc (it's an arc, but due to the minute angle we can aproximate it to a line for the calculation you just did) it's the diameter of the group.
Patrick Graham
Moderator
This really covers it well
http://www.recguns.com/XIIC4.html
one inch group at 100 yards is really 0.95 MOA group
http://www.recguns.com/XIIC4.html
one inch group at 100 yards is really 0.95 MOA group
Destructo6
New member
Ah, I think I have it now...
We're measuring the small angle from of an isosceles triangle, whose legs are at the edge of the group, not a right triangle whose long leg is perpendicular to the target and centered in the group, having the hypotenuse at the edge of the group. That would explain why my calculation was exactly double the value given by the proper definition of MOA.
That's interesting.
[Edited by Destructo6 on 12-31-2000 at 11:08 PM]
We're measuring the small angle from of an isosceles triangle, whose legs are at the edge of the group, not a right triangle whose long leg is perpendicular to the target and centered in the group, having the hypotenuse at the edge of the group. That would explain why my calculation was exactly double the value given by the proper definition of MOA.
That's interesting.
[Edited by Destructo6 on 12-31-2000 at 11:08 PM]
Thank you gentlemen.
Walter, I have never asked this before. (That I can remember).
sensop. I apologize, I was just reading along and thought of this question, and I did not bother to search. Of course, about fifteen minutes after I posted this I thought to myself: "You know I bet somebody else has asked this question and I just forgot."
I'm going to feel really dumb when I look at your list and see something posted by me in one of the discussions.
And I will be honest, I wanted a technical definition because I am writing a small work of fiction that is very gun related and I just thought that Minute Of Angle sounded like a really cool title.
Walter, I have never asked this before. (That I can remember).
sensop. I apologize, I was just reading along and thought of this question, and I did not bother to search. Of course, about fifteen minutes after I posted this I thought to myself: "You know I bet somebody else has asked this question and I just forgot."
I'm going to feel really dumb when I look at your list and see something posted by me in one of the discussions.And I will be honest, I wanted a technical definition because I am writing a small work of fiction that is very gun related and I just thought that Minute Of Angle sounded like a really cool title.
Michael Priddy
New member
You know fellows,it is really more of a solid geometry problem. If the tip of the cone is at the bore of the rifle and the base of the cone forms an imaginary circle on the target paper with a diameter on one inch, then every hole totally inside the circle would be within a moa. If you have to open up the circle to get all the holes in, it will open up the angle of the cone past a moa. BUT if you can cover them all with a dime, who cares about the math/geometry?