The PAM Syndrome

[Bart B.]

Oft times, there's discussion of what is meant by "precision" and "accuracy." I looked up both words for definitions. Most included the word "marksmanship." So, I blended them all together as:

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The P, A & M Syndrome

Precision is having the firearm make all bullets cluster in the smallest group with a fixed point of aim.

Accuracy is having the firearm center all shot groups on the point of aim wherever it's at.

Marksmanship is the ability to put all bullet departure angles such that bullets strike closest to the desired point on target. Best results happen when both precision and accuracy are as good as possible.
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Comments welcomed.

 

[ironworkerwill]

2 outa 3 aint bad, well, really it could be terrible. I realize that I am the weakest link in the operation.

 

[CLP]

Precision is how close to the point of aim the bullet gets. Accuracy is how repeatable it is.

 

[bullzeye8]

Sounds pretty good but I would maybe change the marksmanship to include something about a persons ability and not just an ability because I always felt marksmanship is a human thing not an equipment thing.

 

[murf]

accuracy: a bunch of holes really close together exactly where you want them.

precision: a tool thing. micrometer precision to .0001"

marksmanship: one third of the total package

murf

 

[ironworkerwill]

Accuracy: bunch of holes very close together
Precision: a hole where you want it.
Marksmanship: putting a bunch of tightly packed holes exactly where you want them.

 

[ChaoSS]

Precision is how close to the point of aim the bullet gets. Accuracy is how repeatable it is.

No, you have that backward. Precision is the repeatability, it's all of your rounds falling into one small hole.

Accuracy is having that hole be where it's supposed to be.

 

[1911 guy]

One man's opinion here:

Other than certain few limited applications where group size is scored, regardless of placement on target, the distinction between precision and accuracy is splitting hairs.

A rifle either puts a given number of rounds into a small enough group to be acceptable or it doesn't. Placement of that group is a function of the shooters ability to adjust the sight system mechanically (clicks) or physically (holdover or holdoff) to impact the target. The "accuracy" part of the equation is, in fact, part of marksmanship.

If my .308 shoots a 1.75 MOA group at a 1,000 yard match, that's fine. If it's a foot off the bull, it doesn't matter if group size is scored. However, taking that same rifle, making no adjustment to the scope or iron sights, into a deer blind would be stupid. The difference between "accuracy" and "precision" is exactly 5 clicks. (well, 4.8 on a typical .25 MOA adjustment)

When working up handloads, do you sell the rifle because they don't immediately shoot to point of aim? After all, it's not "accurate".

I guess what I'm getting at is either the rifle and shooter are capable or not. A good rifle and ammunition shoots small groups. Period. A good shooter puts those groups where he wants. Period. All else is semantics and mental gymnastics. I think it's a case of mathematical concept being applied too far afield from it's home turf. Statistics are useful in theory, but in practice hits count. Misses, no matter how close together, do not.

Reminds me of the accountant, engineer and statistician elk hunting. The accountant shot over the elk. The engineer shot below the elk. The statistician yelled "We got him!"

 

[taliv]

i used to think of it as precision is shooting for group, and accuracy is shooting for score. both of those require marksmanship, unless you are shooting from a machine rest in no wind


now i think of precision in terms of aiming size. aiming at a full size ipsc from 500 yards is not very precise. aiming at the head is more precise. aiming for the right eyeball is very precise. accurate is yes/no. did i hit what i was aiming at?

 

[Legionnaire]

To my way of thinking, a rifle is accurate (repeatably small groups) and a shooter is precise (able to put a shot exactly on target). It takes an accurate rifle to shoot with precision.

Sort of like language. One may have an accurate understanding of the definition of a word, but a good writer uses words with precision.

Or medicine. I want a doctor who diagnoses accurately but operates with precision.

 

[entropy]

One man's opinion here:

Other than certain few limited applications where group size is scored, regardless of placement on target, the distinction between precision and accuracy is splitting hairs.

A rifle either puts a given number of rounds into a small enough group to be acceptable or it doesn't. Placement of that group is a function of the shooters ability to adjust the sight system mechanically (clicks) or physically (holdover or holdoff) to impact the target. The "accuracy" part of the equation is, in fact, part of marksmanship.

If my .308 shoots a 1.75 MOA group at a 1,000 yard match, that's fine. If it's a foot off the bull, it doesn't matter if group size is scored. However, taking that same rifle, making no adjustment to the scope or iron sights, into a deer blind would be stupid. The difference between "accuracy" and "precision" is exactly 5 clicks. (well, 4.8 on a typical .25 MOA adjustment)

When working up handloads, do you sell the rifle because they don't immediately shoot to point of aim? After all, it's not "accurate".

I guess what I'm getting at is either the rifle and shooter are capable or not. A good rifle and ammunition shoots small groups. Period. A good shooter puts those groups where he wants. Period. All else is semantics and mental gymnastics. I think it's a case of mathematical concept being applied too far afield from it's home turf. Statistics are useful in theory, but in practice hits count. Misses, no matter how close together, do not.

Reminds me of the accountant, engineer and statistician elk hunting. The accountant shot over the elk. The engineer shot below the elk. The statistician yelled "We got him!"

Well put.

And I have never forgot the maxim: There are three types of lies. Lies, Damned Lies, and Statistics.

 

[Louca]

Quote:
Originally Posted by CLP View Post
Precision is how close to the point of aim the bullet gets. Accuracy is how repeatable it is.

No, you have that backward. Precision is the repeatability, it's all of your rounds falling into one small hole.

Agree. There are really different kinds of accuracy to be considered. Single or individual shot accuracy is how close that single shot is to the point of aim; group accuracy is how close the center of a group is to the point of aim, assuming of course the point of aim is the same for all shots. Actually in shooting, there is no such thing as the precision of a single shot; precision always refers to comparison to other shots from the same gun at the same point of aim (a.k.a repeatability).

Considering multiple shots only, precision (really average precision) refers to how small the group is whereas accuracy (average accuracy) refers to how close the group center is to the point of aim.

 

[HGM22]

http://www.m4carbine.net/showthread.php?170763-Let-s-Talk-About-quot-Accuracy-quot

With Pictures!

 

[1911 guy]

And still useless. If a rifle is capable of shooting small groups, it's the fault of the shooter, poor marksmanship, that they are not on the target.

You either have a rifle and ammunition capable of the task or not. The shooter is capable of the task or not. There are few situations, all of them specialized competition, where a group off target is of any use at all.

Sorry to sound so combative about this, but there is no practical distinction between the "precision" and "accuracy" in this context. It is a function of marksmanship.

They are indeed different when used properly (this is actually a mathematical concept), but this is an improper use of the terms. Precision, mathematically, refers to how consistent a result is in the presence of bias. Shooting small groups is not a battle against bias, it is management of variables. Thus, the terms has been mis-applied. Useless in the context of shooting.

 

[roval]

As others said precision. Is repeatability as manifested by group size and accuracy is point of aim impacts . With adjustablet sights or scope a gun shooting with precision is easy to turn into an a accurate gun shooting small groups.

For me markmanship is ability to consistently hit your target.

 

[Reloadron]

This subject comes up every now and then. Here is how I view things in the Precision / Accuracy world:



I see precision as a high measure of repeatability in a simple definition. I see accuracy as a measure of unbiased precision. So we can have precision without accuracy. We can't have accuracy without precision.

Here is one old thread on the subject.

There have been several others threads as I recall and some were pretty good discussions on the subject.

Ron

 

[MikeJackmin]

I think the correct terms for these concepts are calibration and repeatability, but few shooters would use those words.

Imagine we were discussing an air pressure gauge instead of a rifle. Suppose I apply exactly 30.000 psi to my meter, and I get some readings over time that vary by a few hundredths, and are centered around 31.000. The calibration is off by one, and the repeatability is within a few hundredths. The distinction is specific and clear.

You could take it a step further and talk about the statistical variability of that few hundredths - is it a nice bell curve, and what's the standard deviation? - and we could talk about how the first reading differs from later readings, just like we talk about shots from unfouled bores. If it matters, that stuff can be very interesting, and it gets just as complex as it need to.

There are experimental physicists who do things like taking two atomic clocks and putting one of them about a foot higher than the other. The one that's slightly higher is under slightly less of the earth's gravitational pull, and in our relativistic universe, that means that time itself is actually passing just a tiny bit more quickly there. They can actually measure this difference. I imagine their conversations of this topic can be very detailed.

http://www.popsci.com/science/article/2010-09/superaccurate-clocks-prove-your-head-older-your-feet

 

[Stargazer65]

I'm disappointed. I thought this thread was going to be about spraying PAM on firearms as a preservative/lubricant.

 

[wally]

Precision is how close to the point of aim the bullet gets. Accuracy is how repeatable it is.

Actually this is backward from the engineering/scientific usage.

A stopped watch will be accurate twice a day (it shows the actual correct time) but will not be very precise with an extreme spread of +/- 6 hours.

Accuracy is how close the center of the group is to the actual point of aim. Precision is the size of the actual group.

Generally precision is easier to obtain and demonstrate -- that is why you see many MOA target groups posted, but you almost never see them centered on the actual point of aim.

This is about the closest I've ever come to having POA/POI align for a group:

But its rigged, its good that its a 20 shot group shot right after adjusting POA/POI on a target next to it, but its only 2 moa (at best) ammo shot at 50 yards distance, so the tolerances for success are pretty generous. I might have done a bit better if I'd left the scope at 4X used for sighting in, but I put it to 1X to see if there was any significant zero shift with a power change.

 

[Nom de Forum]

Marksmanship is preforming all the physical and mental shooting skills necessary to be accurate in placing one bullet at or close enough to your aiming point. Precision is the ability to repeat all those physical and metal shooting skills with a gun mechanically capable of placing multiple bullets at or close enough to your aiming point.

 

[1911 guy]

Not to beat a dead horse, but I'll use Reloadrons graphic as an example.

Group one could be the result of a lousy rifle, lousy ammunition, lousy marksmanship, or a combination of all three. These are variables, not bias.

The only difference between groups two and three is simply marksmanship. The difference between the two groups would only be maintained by someone who lacks either the knowledge and/or ability to reconcile the two.

I'll use the example of wind to illustrate between bias and variable in shooting. A consistent 25 MPH wind, with no variation in speed or direction, is bias. It will alter POA/POI by a repeatable amount every shot. However, a wind that alters either speed or direction occasionally is a variable. The result will change periodically. There's no reason other than poor marksmanship to not calibrate (re-zero) for bias. Variable, however, is a changing condition that takes skill to master.

This same bias can be seen when switching from one ammunition to another. They probably won't shoot to the same POI, but groups may be equally small. Let's say the new load shoots 3 inches higher than the old. Re-zeroing is compensating for bias.

In short, precision is a function of rifle and ammunition. Accuracy is a function of marksmanship. FWIW, the images of bullet holes in targets originated in high school textbooks to introduce students to measurement and have nothing to do with shooting. It's an example that's being misused and muddying the waters.

 

[Walkalong]

To me an accurate rifle can shoot little tiny groups over and over.

Precision is how the rifle is put together and the way the rounds are made.

The accurate shooter can put those rounds where they want them. That part is much harder.

Making tiny groups center over an aiming point isn't all that tough, but is a constant adjustment as conditions change.

 

[denton]

Reloadron and the OP have it right.

This happens to be an area that I deal with regularly in my professional work.

Bias is the difference between the mean of a great many samples and the true value. In shooting, this is the difference between the point of aim and the average point of impact. If there is little or no bias, the system is accurate, and it is calibrated. This can be shots scattered all across the target, so long as the average of all shots is at the point of aim.

Repeatability is the amount of variation around the mean. In shooting, this is the size of the groups printed. A repeatable system is precise. In measurement systems (for example, when you do a Gage Repeatability and Reproducibility Study), it is usually expressed as the standard deviation (spread) of measurements about the mean.

If your firearm is accurate but not precise, you're frownin' because it's sighted in and the shots are scattered. The fixes are usually difficult. If your firearm is precise but not accurate, you're smilin' because you're shooting small groups and all you have to do is adjust (calibrate, make accurate) the sights. When you are done sighting in a precise rifle, it is both precise and accurate, which is where you want to be.

 

[Walkalong]

As just described, the accurate rifle can be precise, but it is up to the shooter.

A rifle by its self can only be potentially accurate, the shooter has to make it "precise", both in where the rounds hit and how tightly they group.

A great pool shooter can beat you with a broom stick, just like a great shooter can beat you using a lesser rifle.

But it's all subjective.

 

[taliv]

i dunno, a rifle in a machine rest might shoot 1 MOA. if you're a deer hunter, and that's a gun you paid $250 for, that level of precision is likely to be described as fantastic. if you wanted to use it for a bullseye competition gun, that level of precision is likely to be described as teh suq. It's up to the shooter to make it accurate by zeroing it, and later by accounting for environmental variables (distance, wind, angle, temp, etc)