Accuracy and Precision

[gbal]

Some times it seems the basc distinctions between accuracy and precision are not fully understood by many shoters who nonetheless strive to hit smaller and smaller targets at greater and greater distances,and do so with more consistency. (Litz,.

 

The basics are not new; thus precision is encapsulated by "small groups are good",and accuracy by the knowledge that "a good zero and accuracy prediction are critical".

 

Bryan Litz points out that you get better at hitting targets(assume Vince's point-the first hole is the target in group shooting) if you understand the causes of misses. His mission is to consider the uncertainties and inaccuracies of real world shooting so as to make informed decisions about improving hit %s.

 

Prescision is usually expressed as group size. To hit small targets at long range,rifle,ammo,and shooter have to be capable of firing shots that impact closely together.

Once such grouping is consistently achieved,centering the group on the point of aim (or intended point of impact) is the challenge for accuracy.(Litz).

 

Although these two (A&P) are ultimately integrated,they are usefully considered separately.An example should suffice: if a 1/4 moa rifle/ammo/shooter combination misses a 2 moa target at 1000y,then such a failure is much more likely an accuracy (Litzthan a precision failure,and here it would be an improvement in accuracy that should be the priority.(thus,the miss is more likely to be corrected by an improvement in wind prediction effects,than an extra 50 fps in velocity.)

 

In this example,extreme load development finessing is not likely to be so productive as quite moderate shooter learning. The shooter would do well to invest in a Kestrel,rather than an electronic powder dispenser.Of course,sometimes the opposite holds,and the answer(s) are not always upgrading equipment.

Lets just make a clear note too,that shooter (human) variables pervade both Accuracy and Precision factors- in the above example,it's clear that wind reading needs work,but there is skill too in the use of reloading equiment,or rifle smithing and so on.Differnt skills to be sure,and not all need to be equally possessed by the shooter-or at all (S(he) might just buy top grade loaded ammo.But quality has to come in somewhere in all aspects.

 

OK enough for an opener. The sheer scale of possible improvements,and the implied priorities for achieving them,can be very surprising....in the example,close to 50% improvement via bettter wind reading,maybe less than 2% via load finessing.

 

Note the distinctions are real,but can overlap-sixty years ago I was shooting vermin-a one shot game (they either ran away...or not)...accuracy mattered. But I was also shooting 25y 22rf postal competition-each shot was on a separate bull-smaller by far than the vermin-so even more accuracy,but there were ten such to a card,so it had to be repeated pretty quickly-in effect an approximation to 'group' shooting,the bull being sub calibre.

 

gbal

[brown dog]

Think you're using the wrong terms. Your discourse describes accuracy and consistency. (Precision is related, normally describing a combination of both 'accuracy and consistency' - as in 'precision strike').

[Finman]

The terms are correct, consistency is required in both instances, a bench rest shooter needs to be precise, a target shooter/sniper needs to be accurate.

 

Best wishes

 

Finman

[brown dog]

Umm. No.

[TattooedGun]

By sheer definition, Precision is: "the quality, condition, or fact of being exact and accurate."

 

Neither term refers to repeatability - as in the case of group size.

 

Have to agree with Brown Dog. It's accuracy (or precision - as near interchangeable terms) and consistency that your post refers to.

[gbal]

More over long twaddle.[/qu

 

Sorry John,and Brown Dog (et al)-remiss of me not to give the reference:

 

Accuracy and Precision for Long Range Shooting:A Practical Guide for Riflemen. 2012 Bryan Litz. Applied Ballistics,MI

 

 

 

He has an Aerospace Engineeering degree from Penn State,6 years USAF research on air to air missile design,mathematical modelling and simulation.

He is currently Chief Ballistician for Berger Bullets,and a very active and successful national and international long range shooter.

 

As he says in introducing these two key terms,many shooters do not seem to understand the basic distinction between accuracy and precision very well. That's on page 1,of 212pp

 

 

g

[Offroad Gary]

My rifles are consistent. (And accurate), i wouldnt have a clue if they were precise or not!

[That bald headed Geordie]

I like women breasts and nice rifles. So pleased I am simple and basic folks.

But George, keep 'em coming, but I did warn you about your word spacing to improve the readability for us non graduate types . I will still talk to you and be kind!

[gbal]

Let me say that I did look up quite a few 'definitions' of accuracy and precision,mainly googled,and most were not as clearly expressed as the ones presented in the OP,and were somewhat inconsistent. I did not expect the OP to be contentious,as the descriptions of A&P were clear,and directly related to shooting,at least a good starting point,but then I've read the book,which delivers more than most.I did somewhat expand the human(shooter) factor,though it's not new,and made a plea that we all avoid partisan bias for any particular shooting discipline,and respect the various skills required,and differing operationalising of 'accuracy' and 'precision' in different shooting disciplines. "Our ''accurate' is more accurate than your 'accurate'-gentle fun is OK,but not very constructive,if the aim is to improve efficiently-the goal Bryan states.

We make better progress,with informed discussion.Or just read all 212 pages-they seem well proof read. :-)

As light relief,how about the All Backs...NOT a typo,a succinct definition of "improved progress" via A&P..and muscle.
Y ob't servant,
glab

[TattooedGun]

 

 

Bryan may have made good points, but I don't think that your summary in isolation comes across in the same manor that you may have read Bryans book.

 

Could it be a 'Precision rifle' will shoot precisely (Made to tighter tolerances, set-up precisely and ammunition tailored to exacting measurements) whereas an 'accurate rifle' will shoot accurately (factory rifle with factory rounds).

[Deserttech Europe]

Writing style aside, try and understand what gbal is saying, i think his initial post is 100% correct.

 

Looking at it as an academic may turn some people off but it doesn’t make it incorrect, any more than not understanding the ballistic formulae that your phone/kestrel/charts/pc say makes them incorrect.

 

Dont mean to piss in anyone’s porridge....

 

Ewen

[Finman]

Umm. No.

Eloquent...how about, rifles are manufactured to be precise, but it is the scopes that make them accurate? In other words, precision refers to the ability of the rifle to group tightly (else it is imprecise) but it is the aiming that makes them accurate. In order to be accurate you need consistency (in ammo, shooting technique, conditions etc). To be precise, you need a well manufactured rifle (and ammo). With that in mind, you can be precise without being accurate, but it is hard to be accurate without being precise...

 

Finman

[brown dog]

It's all very simple; and no one needs to try to 'invent' new meanings for long-defined and universally applied external ballistic terms:

 

 

 

[just deleted what I wrote: realised I'm confusing 'precision' as in precision & long-range strike -which require accuracy & consistency- with the engineering/stats concept of precision - which doesn't require accuracy]

[Shuggy]

Circular Error Probability: the circular area around an argument within which a thread has 50% chance of landing.

[brown dog]

Circular Error Probability: the circular area around [the aimpoint of] an argument within which a thread has 50% chance of landing.

 

[Brummy Mark]

Accuracy - hitting the target

Precision - consistently hitting a target within the target

[gbal]

Tatooed Gun-

Not completely sure that saying an accurate rifle is accurate,and a precison rifle is precise,takes us far towards Bryan's goal,and misses Bryan's point that the two are not the same,though some rifles are both-as I understand,on second reading,you mean that a higher level of accuracy than factory is precision,found in custom rifles- something like .5 is accurate .2 is precision? While on average,this summarises factory/custom performance it's not what Litz is about.His A&P are not 'one is just more'of the other'-they are different concepts-and can be independent,and should at least be analysed that way. As shooters here say,shooting a group (P) isn't the same as hitting a varmint(A) -not always respectfully,alas.

Brummy Mark-yes,that's brief but gets some of it-I think Bryan's book expands a bit in developing strategies for improving both,and a detailed methodology (WEZ analysis).Someone may summarise it,if we proceed.

BD - Litz,in clear pictures which are consistent with Bryan's definitions of the terms,though he has more to say on operationalising -and a lot more on both topics in his next 211 pages. The concepts seem reasonably agreed,as ever different terms may be used.Bryan at least is talking about modern rifle performance and how to improve it. His usage seems to me precise and accurate and consistent,valid and reliable,and allows considerable development of the ideas,especially linked with WEZ statistical analysis.Sorry if your domain calls WEZ something else,but a rose by any other name....oops that's 'twaddle' for some.Poor Shakespeare.

Finman- I agree,and there are several ways to analyse these topics,useful for differenct purposes. I tend to think of intrinsic rifle/ammo potentials for both accuracy and precision as the 'manufacturing' aspect,improved by fine tolerances,good homeloading-all that stuff;and then there are aids to getiing that intrinsic performance out of the inert rifle/ammo-what a good trigger/stock help us do-and of course 'us'-the more skilled the actual shooter-and the more in harmony wih the equipment -the more performance can be shown.Wind reading etc come in this latter too- human shooting skills.
But it's not the only way to skin the cat....which isn't Shakespeare.

What helps us agree and make progress is to take good concepts from wherever and see if they can be usefully applied. Litz use of WEZ seems an outstanding analysis of shooting error,and where to focus effort on improving.If anything else can add,then so much the better.

As said,anyone who has misgivings about page 1 could usefully suspend judgement,and read on. Or just get cerakoted- that's legitimate too. Baldie gave some (anatomical) quotes. :-)

I have read Litz,and think it has much of value. Still interested in other well founded views though.
Isn't that what we do here?Well some of us- there is no compulsion.
atb
g

[gbal]

BD- respect-I did look at several useages of A and P-the engineering one for P seemed more about fine tolerances in machining /measurement etc being repeated...of course that is a factor that contributes to rifle P and thence A. But Litz isn't about how to cut metals.

 

"Precision strike' of course is two words,and that often matters (see below)... is 'precise strike' gramatically (but not dramatically) better.... macht's nicht....job done,either way!!

 

order effects: a 'Venetian blind' has only a little in common with a 'blind Venetian'.

Academics who study word meanings often get up to semantics/some antics :-)

 

g

[brown dog]

Well, my external ballistics experience has always held the ability of a weapon to place its shots together as 'consistency';

hmm, if we're using 'precision' to quantify how we describe the repeatability of shots:
Take two 2 inch groups:
One of 1000 rounds.
One of 5.
Isn't the first 2" group more statistically precise than the second 2" group?!

(And what if I measured the 1000 round group with a ruler marked only in whole inches, and the 5 round group with a micrometer?!! )

[gbal]

Matt,being Sunday,I'm more in Rugby mode.

 

But at least to a good approximation,your description of 'consistency' seems close to Litz' 'precision'-putting shots close together.

 

He does -correctly,I think- consider shooting as a probabilistic event-hence the WEZ analyses.These seem informative. Accepting this,I think the 2 inch groups would be equally 'precise'-though not of course remotely equally probable.Precision would vary in so far as the number of shots NOT in the group varied-misses matter,more sometimes than others-that's signal detection theory,and another paragraph another time.

you would get into some complexities with 2 shots out of 1000 out,and 1 out of 5 out,but that is why inferential statistics exist-to give some handle on this. Of course this scenario is extremely unlikely....

 

The measurement issue is easier-the ruler is just a less exact/precise method of measuring small distance accurately (as P and A are used in measurement theory.)-it will lead to more error,on average,and this will correlate inversely as size reduces,below the interval of the tool (inch,versus ten thou say).

Pause for coffee.

 

Similar issues arise in eg human factors tests-if a test is indeed neasuring what it purports to measure,it is "valid",and if it measures the same each time (for the same person) it is 'reliable'.Validity can get contentious (think intelligence),reliability less so. I am sure lay desriptions migh refer to 'valid' as 'legitimate/proper/good' etc...what matters is the concept...like consistency/precision ?

 

As you know.litz goes on to look at improvement in statistical terms too-essentially hit percentages on specified targets under specified 'confidence' conditions (he means shooter skill,A&P,not 'confidence ' limits as in statistics)..but whatever ,the concept is sound,useable and shows the number of not so precision strikes very clearly when plotted....worth a thousand words (once the underlying methods are described). Tally ho.

 

g

[brown dog]

George, I was being a little facetious about the many meanings of the word 'precision': Increasing sample size does increase statistical precision - as sample size increases, the standard error decreases ie your results become more precise.

 

as one of my brats just idiot checked me: 'It's taking out the randomness, it's the difference between saying 2 out of 3 people like dark chocolate based on a survey of 3 people, compared with a survey of 3 million people" !

 

hmm, if we're using 'precision' to quantify how we describe the repeatability of shots:
Take two 2 inch groups:
One of 1000 rounds.
One of 5.
Isn't the first 2" group more statistically precise than the second 2" group?!

[Big Al]

[Admin edit: Al - you're right. Thread pruned accordingly]

[brown dog]

Eloquent...how about, rifles are manufactured to be precise, but it is the scopes that make them accurate? In other words, precision refers to the ability of the rifle to group tightly (else it is imprecise) but it is the aiming that makes them accurate. In order to be accurate you need consistency (in ammo, shooting technique, conditions etc). To be precise, you need a well manufactured rifle (and ammo). With that in mind, you can be precise without being accurate, but it is hard to be accurate without being precise...

 

Finman

 

Just re-read the thread. Yes, I'd buy most of that, but I don't like the 'precise' word in this context .......too many varied colloquial understandings of what it means as well as too many varied nerdy nuances on what it can mean...

 

....and we all know that a 'precision strike' is putting a munition dead centre of an ISIS meeting, and is not grouping 3 JDAMs into a single hole, but two streets away from the target !!

 

...so I'll be sticking with 'consistency & accuracy'

 

 

 

 

Returning to George's opening point. I'm not sure that Litz is saying anything deeper than the sort of expression that says something like 'the rifle's more accurate than you can shoot it' (but correcting the use of the word 'accurate'!).

After that, it sounds as though he's trying to quantify what's known in long range fires as the 'error budget'.

 

I'll do a starter for ten:

 

At a given range, work out your deflection -in inches at the target- for every 1 mph error in your assessment of wind.

Then estimate how accurate your wind assessment is (eg 'I think I'm right to within +/- 5mph)

Do the maths to work out what that +/- 5mph means in inches at the target.

Add that full span of possible wind deflection error to your weapon system's consistency at that range (ie your estimate of it's 'ideal world' group size).

With the two values combined, you now have a more 'accurate' assessment of how dispersed your rounds are likely to be than when considering weapon system consistency alone.

[ds1]

George, the terms to me seem abstract, or at least relative (not grandma) eg the difference between a .2 moa or .3 moa rifle for tactical shooting matters not but does matter to benches shooters, hence accuracy is relative to purpose and the biggest argument over statistical analysis shooting wise is between 3 and 5 shot groups - both of which suck.

 

I know what accuracy and precision are when I see them Accuracy comes from consistent repetition of good training which I guess is why we practice.

 

Precision is the cold bore shot

[MrCetrizine]

The way I've always seen it, rightly or wrongly is this:

 

Accuracy is hitting an enemy at 1000 yards, precision is hitting an enemy standing between two friendlies at 1000 yards.