MOA Confusion

[charliedontsurf334]

I am trying to understand MOA as it relates to firearms. I was always of the impression that 1 MOA is roughly a 1" diameter circle at 100 yd, 2" at 200 etc.

I have a Springfield M1A Standard that I consistently get just under a 2" diameter circle at 200 yards. I have read on this forum that the M1A rarely gets under 2 MOA, so I'm thinking that maybe MOA is calculated by the Radius or the Circumference of a circle.

I get confused by reading a lot of math on various websites so my basic question is:

Is an MOA
a) a 1" diameter circle at 100 yd?
b) a 1" radius circle at 100 yd?
c) a 1' circle in circumference at 100 yd?

[ocabj]

http://en.wikipedia.org/wiki/Minute_of_arc

[Dead*Reckoned]

It would be the diameter of the group size, measured from the center of the bullet to center of bullet.

[charliedontsurf334]

Thanks a lot of those websites just say a 3 shot group, and I guess it is assumed to be assumed you know what that is defined as, but I just wasn't sure and from what I'd read, and it seemed too good to be true that my my M1A shot 1 MOA, but I guess you get lucky sometimes.

[dieselpower]

diameter.

center to center of the farthest.

2" @ 200 yards is a 1 MOA group.

[TimRB]

Others have explained the meaning of "MOA". I would like to point out that if you have a 3-shot group that is inside 1 MOA, chances are VERY slim that your rifle really is a 1MOA rifle. Probably more like the 2MOA you read about. This is all due to the way statistical variation works.

On the other hand, if you shot a 10 or 15 round group that was all inside 1MOA, it would be good evidence that your rifle really is a 1MOA rifle.

Tim

[tdc57]

Here is an example, I shot this target at 300 yards with a ten shot group. (Please ignore the flyer) LOL..



If I measure out between the two centers that are the farthest apart I’ll get my MOA for this shot group. It’s just over 2.5” at 300 yds, so my rifle with this round (yes I reload) was shooting under 1moa.





At 500 yards I should still be grouping under 5”, if I want to hold my MOA under 1

hope that helps.

[Fjold]

You never ignore flyers, they are part of the group.

[captbilly]

1 MOA is 1 minute of angle

I minute of angle is 1/60 of a degree, 1 second of angle is 1/60 of a minute of angle, or 1/3600 of a degree. It is really that simple. It turns out that for small angles a degree works out to be a linear distance of about 1/60 of the distance. So for example at 100 yards one degree is about 1/60 of 300 feet with is 5 feet (or 60 inches). Since one minute of angle (MOA) is 1/60 of a degree that means that 1 MOA is 1/60 of 5 feet (or 60 inches) which is 1 inch. So 1 MOA at 100 yards is about 1 inch. Normally if we are referring to accuracy of a gun we mean that a gun capable of shooting 1 MOA will shoot all the bullets within a circle that is one MOA across which is about 1 inch at 100 yards. Since bullets have a certain diameter we don't measure across the outside of the bullet holes, but to the center of the bullet holes, when figuring the number of MOA accuracy.

If shooting at 25 yards 1 MOA is a pattern of bullets that is .25 inches across plus the diameter of the bullets you are using. A 1 MOA group of .223 ammo (actually .224" diameter) would be a group that would entirely fit within a circle .262 inches (1 MOA at 25 yards) plus .224 inches (diameter of bullet) or .474". At 100 yards the group would have to be 1.047 plus .224 or 1.271 inches, to be 1 MOA. Just remember that MOA is an angular measurement, not a linear measurement, and the scaling with distance makes sense.

Though many people shoot 3 shot groups to measure the MOA accuracy of their gun, the statistical significance of only 3 shots is very low. When a law enforcement or military agency specifies a minimum MOA that their rifles must shoot in order to qualify for a sniper rifle contract, they will shoot many many shots that all must land within specified MOA x 1.047 (plus the diameter of the bullet they are using) in order to determine if it qualifies. To have good statistical significance you would probably want more like 10 shots in the group, but even then you wouldn't really consider a rifle to be a 1 MOA rifle if it would sometimes get you a 1 MOA group of 3 or 5 or 10 shots, but not at other times. Random chance would essentially guarantee that sometimes even a truly crappy rifle would put out 3 shot MOA groups, but only a really fine rifle will put out even 1 MOA groups every day, every time you try it. A true 0.5 MOA rifle is a truly rare piece of equipment, but you will see people claiming that their rifle is capable of 1MOA if they once got a 1 MOA 3 shot group out of it.

[charliedontsurf334]

Well I've gotten quite a few 1 MOA 3-5 shot groups prone supported with a bipod. It's not just once.

[killshot44]

Every time. Five shot groups. That's an 'MOA' gun.....

[xrMike]

Thanks a lot of those websites just say a 3 shot group,

• 3 shot groups NEVER count and you only embarrass yourself by showing them to others
• 5 shots don't count either, but many are willing to pretend they do on the interweb, just to make you feel good
• 10 shots is the real-deal indicator of equipment and shooter skill

[captbilly]

That is very good, and quite believable.

Well I've gotten quite a few 1 MOA 3-5 shot groups prone supported with a bipod. It's not just once.

Many M1As are 1 MOA guns, but these are generally tuned rifles with special barrels and triggers, etc. The 2 inch groups at 200 yards that you refer to in your original post would be 1 MOA by the way, not 2 MOA. It is entirely possible to get a really accurate gun that shoots better than other guns of a similar type, it is sometimes just the luck of the draw. The M1A is a fine gun that is good enough to serve as a sniper rifle if properly set up.

As to you getting quite a few 1 MOA 3 to 5 shot groups. That is some really nice shooting, and you very likely have a 1 MOA gun, but to truly be that accurate it must be able to shoot 1 MOA all the time. Of couse there will be times when you won't be shooting well, and that doesn't mean the rifle can't shoot 1 MOA. And there will also be times when you have some crappy ammo that just isn't consistent enough to shoot 1 MOA, and that also doesn't mean that the rifle can't consistently to 1 MOA. If you find the right ammo, and you go out ten days in a row and shoot 10 shot groups in under 1 MOA then you have a real deal, for reals (as my kids would say) 1 MOA gun, and that is quite rare, much more rare than most people realize.