Accuracy versus Precision

by VonKarman Thu Oct 04, 2018 11:28 pm

The words “precision” and “accuracy” are often used interchangeably, and there is no inherent error in doing so. Indeed, dictionaries often use one to define the other, as equivalent synonyms.

However, I believe there are advantages for the shooting community to adopt definitions of “precision” and “accuracy” from science and industry, which attribute differences to their meanings. These more refined definitions, in a shooting context, may be:

Precision = the size of a shot group, independent of the spatial relationship of the group relative to the intended target; and
Accuracy = how well a shot group is centered on an intended target, independent of the size of the group.

I believe the distinctions between these definitions are demonstrated well in the following graphic, taken from a Guns and Ammo forum post.

Accepting these definitions, I believe we can make the following useful conclusions:

Ammunition has no inherent accuracy. Although ammunition paired with a particular firearm has inherent precision, how well a shot group centers on a target has little or nothing to do with characteristics of the ammunition.
A firearm with adjustable sights contributes little or nothing to accuracy errors when the sights are properly adjusted for a particular shooter, acknowledging that a sight setting for one shooter may result in a bias error when used by another shooter - an issue of reproducibility.
Accuracy of shots on target is almost exclusively the result of how a person uses a particular combination of firearm and ammunition.
The precision in which a person executes their shots adds to inherent precision of the firearm and the ammunition to yield the overall precision of the shot group.

I apologize if this topic has already been addressed in another thread, but I could not find such a thread by a text search of this forum. In turn, I decided to start a new thread, because I thought this topic might invite interesting and helpful discussion.

by CR10X Fri Oct 05, 2018 7:18 am

4. The precision in which a person executes their shots ~~adds to~~ can only equal or detract from the inherent precision of the firearm and the ammunition to yield the overall precision of the shot group.

The discussion has been made before, but in different terms than here:

(1) Learn how to adjust the screws in your brain to train to call the shots and shoot groups = "Precision".
(2) Learn how to adjust the screws on the gun to center the group = "Accuracy".

Which is why a shooter with a 1.0 inch gun and load that does not train, cannot call the shots, does not see what is actually happening during the wobble, and cannot repeat his process consistently WILL ALWAYS get outscored by a shooter with a 3.5 to 4 inch grouping gun and load that does those things.

CR

by GerhardG Thu Oct 11, 2018 12:05 am

CR10X wrote:4. The precision in which a person executes their shots ~~adds to~~ can only equal or detract from the inherent precision of the firearm and the ammunition to yield the overall precision of the shot group.

The discussion has been made before, but in different terms than here:

(1) Learn how to adjust the screws in your brain to train to call the shots and shoot groups = "Precision".
(2) Learn how to adjust the screws on the gun to center the group = "Accuracy".

Which is why a shooter with a 1.0 inch gun and load that does not train, cannot call the shots, does not see what is actually happening during the wobble, and cannot repeat his process consistently WILL ALWAYS get outscored by a shooter with a 3.5 to 4 inch grouping gun and load that does those things.

CR

What a perfect reply! I am new in Bullseye and for a couple of weeks prior to this thread, I have been saying the exact thing as CR stated. I have been checking out scopes that I may buy a good one to spot verify my shots as I call them and write down what i expected and then record what happened. This way I can teach my muscles and time my reflexes.

by BEA Thu Oct 11, 2018 1:08 am

I do not find the words accuracy and precision to be used interchangeably. Accuracy refers to a result. Precision refers to the shot process. Not to be insulting, but you could be an engineer and if you are spending much time thinking about this, you are lost in the weeds and likely not reaching your potential as a shooter...but your enjoyment may be in the analytical process rather than scores...either way, make yourself happy and bless your heart. Anyway, I will take the bait and speak as it applies to shooting. Ammunition certainly can have inherent accuracy depending on the quality of the components used and the precision with which those components are assembled . Accuracy refers to the capability of the system (gun/load) to repeat itself from a fixed position in terms of shot placement (result). Precision refers to the exacting effort (process) that the shooter must put forth due to the size of the area that must be hit in order to get the maximum score...in other words, you have to try harder to do exactly the same thing every time in order to hit a small area. Not only is it important that you hit the target, but where you hit it is important. Target one is very accurate and very precise...but adjust the aiming point. The shooter/system did a great job of repeating the shot process. The ammunition was great in terms of repeatability. Target 2 may not be accurate because from a fixed position, the load/gun combination is not capable of the repeatability needed to achieve a perfect score. It may be very precise if the shooter was successful in duplicating the shot process each time. The opposite could be true too. Target 3 is a severe breakdown of one or both objectives. In terms of accuracy and precision, the only targets that can be positively determined what occured are 1 and 4. IMO...I want to shoot higher scores, so I will go dry fire some and stay out of the weeds. Weeds make me itch.

by Jack H Thu Oct 11, 2018 2:39 am

by bdas Thu Oct 11, 2018 4:14 pm

I think most people would (if they thought about it) disagree with the OP's definitions of accuracy and precision, and he's also confusing it by only talking about groups, rather than individual shots.

Most people would define the accuracy of a gun/ammo as the deviation of the point-of-impact (POI) from the point-of-aim (POA) assuming the gun is already sighted-in. If the gun is aimed at the bottom of the 5 ring when fired, and the bullet hits the center of the bullseye, that's not good accuracy; that's terrible accuracy, albeit masked by tremendous luck. In that sense, the gun itself does have a level of accuracy, as does the ammo (and the combination of the two).

Precision, on the other hand, is usually defined as how close something is to ideal, especially repeatably. So, in some senses, precision and accuracy ARE interchangeable synonyms (ideal accuracy is when POI=POA), but in other senses, they are not.

So, I guess what I'm saying is that I don't think the given definitions actually match how the terms are used in science and industry, and I don't see what advantages there are for the shooting community by adopting particular (especially atypical) definitions of those terms. If anything, having a sizable segment of the shooting community adopt those definitions would make discussions more confusing. You have to keep in mind that in the real world, people are constantly moving in and out of the "shooting community"; it is not a static population. I understand the concept of jargon, but it works best when it is used by a somewhat-uniformly-trained population, and almost never works well when it tries to refine terms that are already in common usage. Consider the concept of precision as it relates to significant digits in measurements... how's that working out for everyone? Language is messy.

Dave

by **Wobbley** Thu Oct 11, 2018 4:24 pm

Potato, potahtoe....

I have 3 questions:
1 Is the ammunition accurate enough (in my gun)?
2 Is the gun accurate enough ?
3 Is the shot where I put it. .

Items 1 an2 can be determined with testing.

Item 3 can be determined with my call of the shot and it’s placement on the target. If it is then it’s a precision shot. The shooter needs work. If it isn’t then either the gun/ ammo or the shooter needs adjustment.

by Jack H Thu Oct 11, 2018 4:43 pm

by **PhotoEscape** Thu Oct 11, 2018 4:59 pm

User name of the OP and the way the post structured points to relationship to famous mathematician and aerospace engineer Theodore Von Karman. Shocked

I'm finding this topic is rather theoretical in nature, as for practical application, I tent to agree with BEA here, differentiation should be made between process, - after all BE is called precision shooting for a reason defined in stated ultimate goal - 2700 points, and practical execution by particular set of tools/skills. Latter includes shooter, gun, ammo and other variables, like atmospheric conditions, mood, etc. So, IMHO, process of "Precision" will equate "Accuracy" when result of 2700 is achieved.

Otherwise from machining world, - 100% of parts withing relatively large sample turned to size with +/- 0.00000" tolerance is the best definition of "precision". Such is possible only in theory, and would be defined as a process, as it must outline all conditions for being able to achieve such an absolute result. Practical results in achieving "precision" is ACCURACY, and can be easily measured. I.e. recent 2663 shooting by John Bickar is ~98.63% of being "precision".

That's my two cents.
AP

by VonKarman Wed Oct 17, 2018 2:51 am

CR10X wrote:

(1) Learn how to adjust the screws in your brain to train to call the shots and shoot groups = "Precision".
(2) Learn how to adjust the screws on the gun to center the group = "Accuracy".

I like this explanation because it is both descriptive and memorable.

by VonKarman Wed Oct 17, 2018 3:14 am

CR10X wrote:4. The precision in which a person executes their shots ~~adds to~~ can only equal or detract from the inherent precision of the firearm and the ammunition to yield the overall precision of the shot group.

Thank you for your comments and proposed edit. I see there is room to clarify the point I was trying to make. I was thinking "precision error," but ambiguously wrote just "precision." I see how one could interpret "increasing precision" to mean smaller group size, but I was intending "increasing precision error" to mean larger group size.

What do you think of:

4. The precision ~~in which a person executes their shots~~ error attributable to a person's shot process adds to inherent precision error of the firearm and the ammunition to yield the overall precision error of the shot group. ?

I was thinking how precision errors add by the square root of the sum of the squares, and in the shooting context:

overall precision error at the target ("size of a group shot off hand") = square root [ (precision error attributable to person's shot process)^squared + (precision error of ammunition and firearm combination ("size of a group shot from a vise"))^squared]

And yes, I agree with you that the combination of firearm and ammunition sets the minimum precision error at the target, and the shooter can only add additional precision error to that minimum - can't reduce it. This idea is captured by the math above that describes how individual sources of precision error add to yield the overall process precision error.

I may be attacked for introducing math here, but I like the math.

by BEA Wed Oct 17, 2018 10:26 am

Well, I think we have gotten to the bottom of it. Here is my summation. Since math is science, and your math is rather basic, we will call it Basic Science or BS. And there is talk of "precision error" which I equate with "precisely wrong." Then your talk about square roots which involves whole numbers brings me to the conclusion...your BS about square roots and round wholes is precisely wrong. Actually the thought of square roots and round wholes pains me, but my intellect is lacking I guess. So, you are perfectly right about being precisely wrong. I am not impressed easily, but your BS is admirable. I am sure everyone here is equally impressed.

by jmdavis Wed Oct 17, 2018 11:31 am

When you think that the quiet one really is quiet, he will surprise you.

by 1joel1 Wed Oct 17, 2018 12:24 pm

jmdavis wrote:When you think that the quiet one really is quiet, he will surprise you.

That sounds precisely accurate!

by dronning Wed Oct 17, 2018 2:09 pm

CR10X wrote:4. The precision in which a person executes their shots ~~adds to~~ can only equal or detract from the inherent precision of the firearm and the ammunition to yield the overall precision of the shot group.

OK let's fling it out another level.

There is a possibility (not probable) that a shooter could actually improve on the guns capability IF and only IF the shooter offset the guns random error with his/her exact opposite random error for every shot to get potentially (not probable) a single hole group at 50 yards.

- Dave

by jmdavis Wed Oct 17, 2018 2:34 pm

The story that I have heard second hand from former AMU Gunsmith Bill Adams, is that Blankenship had a gun that was due for rebuild. But, he was shooting 2600-2650 scores with it and regularly winning matches. He didn't want to give it up. When ordered to turn it in, it was tested and they found that it was shooting 3.5 to 4 inches.

by Olde Pilot Wed Oct 17, 2018 3:56 pm

The same story has been told about Zins. Brian: is true?

by bdas Thu Oct 18, 2018 4:53 pm

jmdavis wrote:The story that I have heard second hand from former AMU Gunsmith Bill Adams, is that Blankenship had a gun that was due for rebuild. But, he was shooting 2600-2650 scores with it and regularly winning matches. He didn't want to give it up. When ordered to turn it in, it was tested and they found that it was shooting 3.5 to 4 inches.

Assuming you mean a 45 caliber gun that was shooting 3.5 to 4 inch groups at 50 yards (and thus, presumably 1.75 to 2 inch groups at 25 yards), this is certainly possible. With a hold + trigger control such that the dot is always in the 10-ring when the gun goes bang, and using a .45 caliber gun shooting 4-inch groups at 50 yards, you will score somewhere around 2619 (97%, high master). Same scenario with a 3 inch gun improves the score to around 2640 (and a 2-inch gun bumps it to 2658). So, yeah, a 3.5 to 4 inch gun with a 10-ring hold and very good trigger control will get scores in the 2600-2650 range, but someone with those abilities can buy a lot of very tough points with a better gun.

I wish I had a 10-ring hold.

Dave

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