What Does 0.5 MOA Mean?

[CharlieNC]

I find it interesting to often read "my rifle shoots 0.5MOA all day long", especially in the context of mid to long range shooting. There must be quite a number of championship shooters lurking out there! But I have been working on a set of calculations to predict scores (like F-class) and group sizes for a given performance level of shooting; this is based on the radial distance measurement which you may have read about. A simple but fundamental question which arises is how do you attempt to state some level of shooting performance? For example for one particular case the expected group size is 0.7MOA 50% of the time, 0.8MOA 75% of the time, etc up to 1.2MOA 99% of the time. Obviously we all experience variable group sizes like this, and may tend to dismiss those which are worse, when in fact all this comes from the same level of performance. Interestingly it appears that scoring provides more consistent answers than group sizes. So what is your interpretation/insight regarding how to express shooting performance in a clear, concise manner? Soon I will attempt to write up these calculations with respect to real world applications.

 

[Terry]

A Minute of Angle (MOA) is an angular measurement.

A MOA is 1/60th of a degree.

1 MOA spreads about 1" per 100 yards. (actually 1.047")

1 MOA is a different size at different distances, 8" at 800 yards is still just 1 MOA.

100 yds 200 yds 300 yds 400 yds 500 yds 600 yds 700 yds 800 yds
1" 2" 3" 4" 5" 6" 7" 8"

 

[Ledd Slinger]

A description of a firearms level of MOA performance at a given distance doesn't get much more 'concise' to me. As per your choice of word, it is brief and to the point while being completely descriptive. To be more exact on a description a person can simply provide an actual group measurement.

You can't give predictions on cartridge accuracy because it is way too sudjective to the level of firearm craftsmanship, rifle components, ammo components, the equipment used to make the ammo, and the handloader personal ability to make it. An inherently accurate round like the 223, 308, or 6 PPC can produce record breaking accuracy in a well built rifle, but then can also produce horribly bad groups in a poorly built rifle or with poorly made ammo

As for scoring, it doesn't give more consistent answers for accuracy than group sizes. A good score means the 'shooter' has excellent wind reading abilities and is making the proper adjustments to center the shots. Wind plays a big part of groups sizes as well, but a shooter can make a bad wind call for his entire record group and as long as the conditions stay the same, he may produce the smallest group in the match, but be off in the 7 ring thus producing a low score. Is his rifle less accurate? Absolutely not. In fact it may be the most accurate, but the 'shooter' made bad wind calls.

So not really sure what you're trying to do here? The wheel is round, can't make it any better than that

 

[Sniper338]

ABOVE IS CORRECT!

I measure my group size by measuring the distance from the outside edge to outside edge of the largest part of the 5 shot group... then subtract the bullet diameter...


.5 inch - 5 shot group with a .264 cal bullet = (.5)-(.264) equals .236 so I would call it a .2MOA group



OR most of the time I really dont care about MOA since I dont use anything MOA anyways... I measure the group outside edge to outside edge with my calipers...... .421 inch 5 shot group (example) - and this is how I usually keep track of them all...

 

[CharlieNC]

The question "what does 0.5MOA mean" is tongue-in-cheek. I know what the number means, but what does it mean to use this expression regarding one's long term shooting performance. Does this mean you get that good some of the time, most of the time, all of the time? This is related to the question "well how many shots to qualify a group". What I'm working towards is the individual POI can be measured and the results summarized with an average and standard deviation, and those results are easily used based on the normal distribution to describe the probability of getting different sized groups and scores from this given level of shooting performance. This is similar to B Litz WEZ analysis, but using simple normal probability distribution ( which the radial distance measurements do conform to ).

 

[wolley]

Because of the varying conditions that matches are shot in I don't believe something as concise as radial distribution will ever be useful.

 

[Toby Bradshaw]

The question "what does 0.5MOA mean" is tongue-in-cheek. I know what the number means, but what does it mean to use this expression regarding one's long term shooting performance. Does this mean you get that good some of the time, most of the time, all of the time? This is related to the question "well how many shots to qualify a group". What I'm working towards is the individual POI can be measured and the results summarized with an average and standard deviation, and those results are easily used based on the normal distribution to describe the probability of getting different sized groups and scores from this given level of shooting performance. This is similar to B Litz WEZ analysis, but using simple normal probability distribution ( which the radial distance measurements do conform to ).

Charlie, you must realize that shooters using extreme spreads (with varying N!) aren't interested in statistical power, or don't understand statistics, or both. Have you read the attached? They're more up your alley.

I wouldn't assume that a Gaussian distribution is appropriate for measures of rifle precision in outdoor conditions. A right-skewed distribution of some sort would likely give a better fit.

 

[Berger.Fan222]

I take a 0.5 MOA rifle to mean that that's what the rifle will do reliably at 100-200 yards, before the wind is really in play so that the mid and long range scores come down to reading the wind rather than any equipment issues.

 

[dcali]

Don't overthink it. A 0.5 MOA rifle in the context of long range competition (say, F class), will put 20 rounds inside of 0.5 MOA at short range. It's a measure of the inherent dispersion of the rifle/ammo combination - *in the context in which it is used*. You can get all fancy with statistics, but there's really no point because most people won't understand them, and it's really not worth the effort even if you do.

That's what it means for me, at least.

 

[Berger.Fan222]

I think too many long range shooters are chasing improvements in inherent accuracy when they really need to be learning to read the wind better.

A 0.3 MOA rifle will not score much better than a 0.5 MOA rifle, but either rifle will do much better in F-Class in the hands of a shooter who reads the wind well.

 

[mudpie]

The use of MOA to describe accuracy confuses me. I have a hard time getting my head around using angles to describe accuracy. What is intuitive to me is group size in a common unit, like 2 inches at 300 yards. Am I the only one who feels this way?

 

[dcali]

Same thing. You're just using two numbers to describe an angle instead of one.

 

[Lapua40X]

... So what is your interpretation/insight regarding how to express shooting performance in a clear, concise manner? ...

The number inside the "X" ring ....
All others are flyers :

The use of MOA to describe accuracy confuses me. I have a hard time getting my head around using angles to describe accuracy. What is intuitive to me is group size in a common unit, like 2 inches at 300 yards. Am I the only one who feels this way?

2 inches at 300 yards is approximately .66 MOA. It's just a different way to express the same number. Telling a shooter to estimate what his group should be at 800 yards using the 2 inches at 300 yards model makes the math very difficult IMO. Σ 2/3*8 If he understands that his rifle is capable of .66 MOA then he knows immediately that his 800 yard target should provide approximately 5.3 inch group (.66x8). It is, after all, an estimate. Even those images of calipers over holes in targets that we often see posted in forums are simply estimates. The "precise" center of the holes in the target aren't truly identified in those images.

 

[Ledd Slinger]

... So what is your interpretation/insight regarding how to express shooting performance in a clear, concise manner? ...

The number inside the "X" ring ....
All others are flyers :

The use of MOA to describe accuracy confuses me. I have a hard time getting my head around using angles to describe accuracy. What is intuitive to me is group size in a common unit, like 2 inches at 300 yards. Am I the only one who feels this way?

2 inches at 300 yards is approximately .66 MOA. It's just a different way to express the same number. Telling a shooter to estimate what his group should be at 800 yards using the 2 inches at 300 yards model makes the math very difficult IMO. Σ 2/3*8 If he understands that his rifle is capable of .66 MOA then he knows immediately that his 800 yard target should provide approximately 5.3 MOA group (.66x8). It is, after all, an estimate. Even those images of calipers over holes in targets that we often see posted in forums are simply estimates. The "precise" center of the holes in the target aren't truly identified in those images.

OP, Dan meant that .66 MOA would be aBout a "5.3 inch" group at 800 yards. Not 5.3 MOA group. A 5.3 MOA group at 800 yards would be about 43 inches.

 

[Bryan Litz Ballistics]

Charlie,

I'm with ya; the statement that a rifle is '1/2 MOA' is really subjective and there's little agreement about the criteria for establishing such a statement.

Picture the following scenario. You've got a room full of long range shooters and you pose the question: "how many of you can shoot 1/2 MOA groups at 100 yards?" Most hands will go up. Now ask: "how many of you can shoot 1/2 MOA groups at 1000 yards?" Some hands will go down, and some caveats about wind will be discussed. Now say: "those of you who can shoot 1/2 MOA groups at 1000 yards in no wind, there's a 5" steel plate 1000 yards over there (a 1/2 MOA target). I'd like to bet each of you that you can't hit it with your first shot" My guess is you'd make money.

The above scenario illustrates the difference between accuracy and precision. Shooting a 1/2 MOA group is easier than hitting a 1/2 MOA target. For most shooting applications, hitting targets including scoring rings is the primary objective.

So although I appreciate your question from an academic perspective, what I'd like to ask is, why don't we have a metric to determine a shooters ability to hit targets rather than just shoot groups?

For example, rather than state you have a 1/2 MOA rifle, say: "I can hit 85% on a 1/2 MOA target". or: "I'm 92% on a 5" plate at 1000 yards". In certain disciplines shooters can reference scores, like: "This season I've averaged mid 190's on the 1000 yard F-class target". Who cares what precision potential the rifle has, that's just one (smaller than most think) element in the overall result.

Expressing performance in terms of groups/precision only, to me, is incomplete and only describes precision. So it only makes sense for Benchrest shooters who are competing purely on groups. Why a hunter, F-class or Tactical competitor would talk about precision without mentioning accuracy has always seemed strange to me.
Lots of confusion as to how a 1/2 MOA rifle can miss an E-type at 400 yards. But if you know you're 20% on moving E-types at 400 from the kneeling position, then it all makes sense!

Sorry, still not a direct answer to your question. Just my thoughts on the matter.

-Bryan

 

[CharlieNC]

Bryan I am with you. Since I am working on calculations which lead to your suggestion, at the same time my question is get the perspective of others' definitions as I address group size and the probabilities of such. From Toby's suggestion while the distribution of shots at short ranges by very skilled shooters may be skewed,my measurements certainly confirm unless you are shooting one-hole groups then the results are normally distributed; this makes it easy to calculate the predictions as you suggest. With this basis then you can add the effects of velocity variability, etc on top of that as you have approached with the WEZ analysis. I'm mostly retired and have a a bit of time on my hands!

 

[Ledd Slinger]

This proposed calculation would work in a controlled environment while utilizing a rail gun perhaps. But when you add in the human error factor and wind shifts that can often change in 3 different directions or speed in mere moment while the bullet is en route to a 1000 yard target, things get very unpredictable.

The calculations would definitely be better suited for short ranges in consistent or controlled environments.

Competitons usually calculate aggregate scores and group sizes throughout a season. But if the weather conditions were horrible at every shoot for a given year, usually the shooters aggregate suffers. Then the next year the conditions may be perfect at every event and the shooters aggregate is outstanding. Then there may be a year where you have a mix of conditions. But by that time a barrel will probably be shot out. So what's the point?

This calculation is not far off from trying to predict the weather. Though the same could be said for someone who states their rifle will shoot '1/2 MOA all day long'. But a declaration of MOA is the simpler and more understandable method used throughout all the shooting world. Either way, each statement, whether portrayed in MOA or a percentage, would have to be proved on paper by the shooter in front of witnesses. It is still an interesting read

 

[Lapua40X]

OP, Dan meant that .66 MOA would be aBout a "5.3 inch" group at 800 yards. Not 5.3 MOA group. A 5.3 MOA group at 800 yards would be about 43 inches.

Yeah .... is my face red :-[
Thanks for raising that point. Appreciate it .....

 

[Ledd Slinger]

OP, Dan meant that .66 MOA would be aBout a "5.3 inch" group at 800 yards. Not 5.3 MOA group. A 5.3 MOA group at 800 yards would be about 43 inches.

Yeah .... is my face red :-[

No big deal we all type things wrong sometimes. I think everyone knew what you meant. I just didn't want the OP getting confused

 

[dcali]

There is a reason for, say, F Class shooters to talk about both precision and accuracy. Especially mid range F class. It's because the x ring is about 1/2 MOA. If your rifle isn't capable of at least that with a high degree of confidence, then you simply aren't competitive, even at local matches. In other words, rifle precision is a significant, even limiting, factor in overall performance.

When you look at sling/XTC shooters, it gets less clear with the bigger targets and less stable positions. The shooter matters more and the rifle matters less. You still need a decent rifle, but a very good shooter with a mediocre rifle can still win a match, unlike in F class. An off the rack deer rifle won't do it, but the bar really isn't that high as far as precision goes by today's standards.

Benchrest requires some shooting skill, but the bar set is so high that the rifles need to be top notch to before you can even think about competing. The targets are tiny (a 0.0" circle), and the position does not get any more stable. You need a 1/4 MOA rifle to think about winning those (last I checked at least, I haven't spent too much time following BR in a while).

So it's a matter of degree. Every discipline has a unique blend of technical skill (ammo, rifle, etc) and shooting skill (sight alignment, trigger control, position, etc). Some are more technical than shooting, others are pretty much all shooting.