Measuring Accuracy As Opposed To Precision

That's how I do it. And in that respect, MOA is a radius, not a diameter.

trackskippy said:

That's how I do it. And in that respect, MOA is a radius, not a diameter.

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Moa as displayed on your target is neither a radius or a diameter, it is a straight line , center to center of the bullet holes. At 100yds this distance is just fraction over 1".
The big difference between accuracy and precision is that you are the main variable in precision. A rifle can be capable of MOA groups that do you no good if you can't put them on target.

I do a test with all my hunting rifles. I take them out randomly throughout the year and I will leave them in the garage overnight to acclimate to the cold and then I go shoot one round on the same target and see where that cold bore shot lands. I am in minnesota so that can be anywhere from 90 deg in the summer to -30 in the winter, and yes I do go out and shoot all my guns at -30 deg in the morning in january. A really good rifle with good ammo will maintain its cold bore point of impact over that temp range. Some of them struggle. Especially on the ammo part of the equation. Lets just say some powders that are supposed to be temp stable are not, and primers make a difference. The 2 rifles that I will absolutely trust my life to grab out of the safe and go make a shot with at any temperature a human can tollerate are my Tikka T3 light in 25-06 and my AR15 in 7.62x39. You could glue the scope caps on both of those.

“MOA” [dispersion] is neither a radius nor a diameter.

The angle of dispersion projected by the cone created from the center of the chamber and scribed by the center of the bullet holes is measured in minutes of angle. The group is a projection of statistically realized members of a dispersed population.

So no, MOA isn’t a radius or a diameter. A group radius or group diameter can be expressed as a projection of the angular dispersion, relative to the distance fired, but it’s neither by nature.

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.

it is correct that moa is most properly presented as a cone. For our purposes though at the target distance it is like a slice through the cone.
If you have a 2" group at 100 yards that is approximately 2 moa of precision.
If the center of that group is 3" from the point of aim then you have approximately 3 moa of accuracy.

What this means to you as a shooter -
Precision is inherent in the firearm/ammo. There is nothing short of changing the firearm or the ammo that a shooter can do to improve precision. The shooter

The shooter can not improve precision without changing the firearm or the ammo. If the shooter holds perfectly the best they can achieve is the inherent precision of the firearm. If you want to improve precision the only way to do it is to throw money at it by gunsmith in or replacing.
Precision improvements come on a logarithmic scale. If you are starting with a $100 pawnshop special firearm a little money upgrading can make a big difference.
If - on the other hand - you are starting with an inherently precise platform - like a sub-moa Tikka for example - a tiny improvement will take a buttload or two of money.

Assuming an adequate sighting system, accuracy is primarily improved by improving the shooter. A better scope does not make a rifle more accurate (unless the first one is broken). It just makes target acquisition easier.

what I am trying to say here is you can have a precision rifle and an accurate shooter. Learn your dope. Hit your targets.

Turkeytider said:

Curious as to how folks assess accuracy. Measure POI from POA?

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I measure it as described by group size, measured center of hole to center of hole, at whatever yardage, usually 100 for easy math. Thus I say, “My Remington 760 is a one inch rifle, believe it or not.”
Mostly because I dislike acronyms.


My assumptions…
In rifle country I can move my sights to my point of impact. There is not really a reason to measure from point of aim to impact since they should be one in the same and centered there. Unless there is some test being done in some fashion, i.e. “The Box Test”.

Everyone knows what an inch is here. If I was in Belgium I would use centimeters, I think, I’ve never been.

The rifle is shooting it’s preferred load. I discount flawed ammunition, some count everything. Rimfire shooters are especially ruthless in this regard.

Enjoying the Savage, @Turkeytider?

Practical accuracy to me is, difference between POA and POI. In that respect, to me anyway, MOA is a radius.

The size of the group is based on where I was aiming to outer most round, discounting flyers, not center to center of the spread of the group itself.

I sometimes shoot "one shot groups" with my hunting rifle. I take it and my hunting ammo along to the range with whatever I am shooting and shoot 1 shot at a target with the hunting rifle. After a dozen trips or so have a real good idea where that first shot is going to go.

The rifle is a featherweight and 5 shot groups open up a good bit. But the one shot group over 5 times is smaller so I am well pleased with this rifle.

I think this is a good test of "accuracy".

Once precision is determined - no matter how you measure it - is accuracy any more than a matter of adjusting sights to get to get the center of group to land where you want? If I sight to be 2" high at 100 to increase MPBR, does that mean the gun is inaccurate because POA and POI don't coincide? No. To me, practical accuracy (PA) is about the shooters ability to get the job done. To quantify the shooters ability, I guess I'd take group size from different field positions and subtract the the precision determined at the outset. So from a bench, PA equals precision. If the shooter delivers 3" groups from a kneeling position and the gun has a demonstrated precision of 1", then the shooter is capable of delivering 2" PA. But since both variables are included in the results, the whole discussion is moot: measure group size, know target size and shoot or don't shoot depending on range.

I think we should acknowledge that, by in large, the difference between POA and POI, within the limits of the mechanical precision of the gun and load, is a result of NOT being pointed at the intended POA when the bullet left the barrel.

Turkeytider said:

It appears that there are different interpretations of accuracy and precision and what impacts them. Some think PRECISION ( group size ) is inherent in the equipment while ACCURACY ( POI in relation to POA ) is primarily shooter dependent. Some appear to believe that it`s just the opposite. That`s confusing to a neophyte rifle shooter such as yours truly. Real life example. Say I shoot 30 rounds from my .223 Savage 110. I measure the POI for each in relation to POA. Say The average of those measurements was .7". For practical purposes, is it accurate to say that that is sub-MOA accuracy?

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Thats the way I see it.

The repetitive group to POA is the realistic measure of you, the gun, and the ammo.

To take it a step further, at least from a hunting standpoint, PBR/BSZ, for most people, is probably a better way to look at things too.

One thing for sure..100 yards damn sure isn't far enough to determine accuracy or precision.

PBR...Point Blank Range

BSZ...Batttle Sight Zero

Both one in the same really

Turkeytider said:

It appears that there are different interpretations of accuracy and precision and what impacts them. Some think PRECISION ( group size ) is inherent in the equipment while ACCURACY ( POI in relation to POA ) is primarily shooter dependent. Some appear to believe that it`s just the opposite. That`s confusing to a neophyte rifle shooter such as yours truly. Real life example. Say I shoot 30 rounds from my .223 Savage 110. I measure the POI for each in relation to POA. Say The average of those measurements was .7". For practical purposes, is it accurate to say that that is sub-MOA accuracy?

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You can look at it any way you want, but either MOA or inches, its about the diameter of the of the circle described by the shots, not the radius.

South Prairie Jim said:

One thing for sure..100 yards damn sure isn't far enough to determine accuracy or precision.

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I would disagree with that if you also have accurate chronograph data.

JumboJVT said:

You can look at it any way you want, but either MOA or inches, its about the diameter of the of the circle described by the shots, not the radius.

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We are looking at this different ways. Youre calling it the size of the group itself, Im calling it the size of the group in relation to the POA.

MOA also seems to mean different things to different people. I was a surveyor for a good part of my life. MOA is just that, "Minute of angle", and a predictable deviation/distance off a line at a known distance. 1 MOA is basically 0.03' at 100 feet, or about 0.09' at 300. (Tangent of the angle off the line at a specific distance on the line)

In shooting, that "line" is point of aim, and the "radius", is the radius of a cone, as we arent dealing with a flat, triangular surface. The average radius at the POI is what I call the MOA group, based on the POA.

Group size is meaningless if its not based on the POA, unless of course youre simply trying to shoot a group, and dont care where it lands. You might have a bughole sized group at 100 yards, but if its 3" or 0.25' or so to the left and/or right of POA, to me, thats about a 3MOA group. And its entirely possible, it measures 6". 3MOA, in all directions from POA.

Like human gender identification, accuracy has gotten to be what you want it to be. I do believe the old timers standard of accuracy, the string measurement, was a cruel and exacting method of accuracy measure that was dumped because it took too much time, and probably lead to too many arguments.

The string measurement technique started with the "mark". The shooter made a mark on a flat piece of wood. The distance from the center of that mark to the first bullet center was measured with a string. Shooters gave up a bullet to be used for determining the center of the hole. The string distance between the center of the first shot to the center of the next shot was measured. Then the distance from the center of shot number two to center of shot number three was measured with the string and so on, until the required number of shots was fired. The length of the string at the end of the match determined the winner, the shortest string was of course, the winner.

I have never fired in a string measurement match, but this method allows no mulligans! Offsets and extreme spreads have to be small.

There is an excellent article at the end of the Oct 2014 Shooting Sports USA on group size and accuracy: http://www.nxtbook.com/nxtbooks/nra/ssusa_201410/ This foundational article was written by small bore prone competitors who wanted to shoot perfect scores. In small bore prone a Match is a 40 shot event of two twenty shot targets.

this is a 20 shot fifty yard target



and this is a 100 yard twenty shot target





The typical 1600 round Smallbore bore prone tournament is 160 rounds fired for record, divided up into four 40 round Matches. Therefore the referenced article assumes that a 40 round group is the baseline.

As anyone can see in table six, at least at 100 yards, a five shot group is 59% of the size of a 40 shot group, a 10 shot 74%, and a twenty shot 88%. A three shot group is below contempt, but three shot groups are the current standard for the shooting community because the leaders of the shooting community, that is in print Gunwriters, have convinced the shooting community that three shot groups are an exact measure of accuracy and consistency.

This is another good article on the limitations of five shot groups

Accuracy Testing: Shortcomings Of The Five-Shot Group

by Brad Miller, Ph.D. - Wednesday, September 25, 2019
https://www.ssusa.org/articles/2019/9/25/accuracy-testing-shortcomings-of-the-five-shot-group

one that addresses statistics for accuracy.

Shot Group Statistics for Small Arms Applications

https://apps.dtic.mil/sti/pdfs/AD1034885.pdf

you may have to go to the main DTIC web site and then find it, as Government web sites are consistently changing and churning.

What we should recognize is that Gunwriters are shills for the industry. They really don't want to exhaustibly test the weapons they are given for several reasons. The first is time and materials. Gunwriters are given a flat fee for their articles, DPris said $400, the less they shoot, the less they spend, the more money they get to keep. The less time and material they have to spend on the current article, the more time and less money they have to spend on the next. Based on the compensation rate DPris stated, I think it is obvious that articles are a loss leader for writers, and that they are only doing it for the vanity, and promotion of “their brand”. Another reason for low shot count is even though these guys get weapons that are "worked over", they are not interested in proving the inherent accuracy of the thing, because the inherent accuracy of the thing may not meet the communities' expectations.

And then, they post the largest and smallest group size out of three, three shot groups and then post an “average” group size. What a crock, and totally deceiving! Averaging makes the group size appear smaller. The extreme spread of the nine shot groups they shoot is the size of the largest group. A shooter hits or misses based on the extreme spread not based on an average distance.

Readers then run screaming to the local gunstore to buy a $1200 rifle based on the results of maybe 18 shots. Sure shows how little it takes to induce the buying behavior response.

The shooting community imitate the in print crowd, showing the power of advertizing to shape and mold the public. Readers think these guys are experts, which they really are not, and believe they are objective, which they are not, and believe the influencers are acting in their interest, which they are not. Influencer’s are acting in the best interest of advertiser’s, and always have. Magazines are acting in the best interest of advertiser’s, since the business model of magazines, is that they make their profit through advertisements. Your subscription is more or less earnest money, it does not even pay for the paper and postage! What you read is advertising, nothing more, and shooters proudly showing three shot groups are simply displaying advertising induced behavior. But they are not showing either accuracy or precision, but something closer to the Texas Sharpshooter fallacy.

the more you shoot, the worse it gets







that's why you don't see many ten shot groups being posted. Vanity won't allow it, fragile egos can't take it.

more on this

https://www.everydaymarksman.co/marksmanship/rifle-precision/

https://www.shootingsoftware.com/measure.htm

South Prairie Jim said:

One thing for sure..100 yards damn sure isn't far enough to determine accuracy or precision.

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You’re missing the words “long range” between “determine” and “accuracy,” otherwise you’ve unduly discounted and invalidated the entire book of knowledge for short range benchrest.

It’s not so difficult: group size is precision. Group position is accuracy.

I can say a man is 7’5”, or I can say he is tall. Stating 7’5” is precise, but if he is actually 6’5”, the claim is not accurate. Equally, stating he is “tall,” is imprecise, but if he’s anything above 6ft, the statement is accurate.

Shooting a 1/2moa group anywhere on the page is high precision. Independently, centering over the target is accuracy. And yes, in general, if given a precise firearm, then accuracy is simply a matter of sight/scope adjustment.