Author Topic: accuracy versus precision (Read 1666 times)

borg1 · « **on:** January 06, 2005, 02:04:46 AM »

Hi all,

Accuracy is the commonly accepted description for a rifle that prints tight groups. Usually precision never factors into any discussion. While reading several posts on rifles that shoot tight groups (called accuracy many times in the thread), it dawned on me that i think we're using the wrong terminology.

Ok, ok, i know i am a bit anal, but here goes...

Suppose we have a target at 100 yards.

I fire a 3 shot group which hits 2" low and 2" to the right. All three bullets form a nice 0.5" grouping at that position. This is done 4 more times, all with the same results.

Another person fires a 3 shot group at a different target and all 3 bullets land in the X ring, but the group is 1.25 inches. This is done 4 more times, all with the same results.

From these two examples i would say my rifle is more precise than the other person's based on the fact that my groups were tighter.

Alternately, the other persons gun is more accurate than mine because all his bullets were in the X ring whereas all of mine were 2"low and 2" to the right. I know there are lots of variables influencing this, but overall i think it illustrates a valid point...

My point here is that we too often use the term accuracy improperly when, in fact, what we are describing is precision (group size).

I think any gun can be reasonably accurate, but not all guns can be reasonably precise.

I'd love to hear any comments on this...

MGMorden · « **Reply #1 on:** January 06, 2005, 02:22:14 AM »

Your'e pretty much right. In scientific experiments accuracy refers to the "correctness" of a measure. IE, how close you are to the true value (true value would be bullseye in this case). Precision refers to the repeatability of that measurement; even if it's a wrong measurement, if you can get the same thing over and over then it is precise.

With rifles however, unless your scope and mounting system is off, then any rifle that can shoot precisely should be able to shoot accurately with proper adjustments.

Cottonwood · « **Reply #2 on:** January 06, 2005, 02:28:21 AM »

I think the word your looking for here is, such as in the group you discribed hitting 2" low and 2" right. That group is hitting consisitantly 2"L and 2"R where as the other shooter, and I take it was using the same gun was consistantly shooting a 3 shot 1.25 group in the X-Ring.

Now for you with that rifle, you would have to make your adjustment both vert. and horz. if you were looking for that X-Ring consistant grouping.

I think the key word is Consistant

I will give this example, when my son is using one of my scoped rifles such as my Remington 700 ADL in .223 I can consistantly group a dime size group the size of a dime. But my son shoots the same rifle and consistantly groups low and right. My son is upset because he can not for the life of him group it in the X-Ring, but I can.

The key factor is that it is grouping consistant.

Now if the rifle is held in a shooting vice, and a hydrolic trigger device is used, that is the only way a person can say.... my rifle is accurate, and prints the precise group each and every time shot after shot.

Nightrain52 · « **Reply #3 on:** January 06, 2005, 04:14:47 AM »

Precision-Ability to put 5 shots in same hole. Accuracy-Able to shoot 5 shots you can cover with a quarter or dime or whatever.

handirifle · « **Reply #4 on:** January 06, 2005, 04:50:47 AM »

What they said! :-) :-) :-) :-)

gwhilikerz · « **Reply #5 on:** January 06, 2005, 05:34:12 AM »

After recently receiving a very "concise and precise" language arts lesson from someone here because of what I said I have decided to use whatever word or term I am comfortable with. I don't like nit-picking or one-upmanship. Sorry but I had to get that off my chest. I'm better now though :wink:

Mac11700 · « **Reply #6 on:** January 06, 2005, 05:39:14 AM »

Quote

I fire a 3 shot group which hits 2" low and 2" to the right. All three bullets form a nice 0.5" grouping at that position. This is done 4 more times, all with the same results.

Another person fires a 3 shot group at a different target and all 3 bullets land in the X ring, but the group is 1.25 inches. This is done 4 more times, all with the same results.

From these two examples i would say my rifle is more precise than the other person's based on the fact that my groups were tighter.

Your have to give a complete example of the discription...without leaving who ever is reading what you wrote...in a position to assume what your meaning...ie; were you just shooting for groups...or were you both shooting for score at the bulls eye??? If not..one can assume...the other guys is more precise in shooting X's...even though your gun/load combination may give better accuracy...

The word precise...means exact...or exactly...precision means high quality with attention to detail...accuracy means going to a spot "precisely aimed"

Mac

jeff223 · « **Reply #7 on:** January 06, 2005, 05:58:29 AM »

i guess you lost me on this one?the way i look at it accuracy and precision are one in the same.you cant have precision without accuracy

if you ever looked over a target i posted here that i shot for one of the postal matches you will notice all the groups are above the dot or x ring or what i mean is the point of aim.when you shoot for small groups you dont want any of the bullets hitting your point of aim.your point of aim should never change from shot to shot .now to a non shooter looking at one of these targets they might think i missed the dot or x ring or whatever you want to call it but the bullets are hitting were i want them to.with a 4 click adjustment on the scope the point of impact would be right on the point of aim.you get what i am saying here? :grin:

Badnews Bob · « **Reply #8 on:** January 06, 2005, 06:06:16 AM »

I use a lot of whats known as Kentucky windage, I tend to shoot where it hits to get in the Xring and adjusting later. I'm not very politcally correct eighter. Us good Ole boys don't much care what ya call it as long as you can put meat on the table. :grin:

Mac11700 · « **Reply #9 on:** January 06, 2005, 06:19:45 AM »

Jeff:

Quote

i guess you lost me on this one?the way i look at it accuracy and precision are one in the same.you cant have precision without accuracy

Yes you can...but you have to discribe what your talking about...you can say..."my rifle is accurate"...ok...that means it is shooting where your aiming...

You can say" I make only precision handloaded ammunition"...that doesn't mean it will be accurate in anyones rifle...but that you used the utmost care,highest quality components,and in every step of producing that ammunition,you've done everything possible to make it the "best" that can be...it is the attention to detail...that the word precision means...like any fine product that is produced...it doesn't gaurentee that it will be accurate...it only means it was produced with the highest quality standards...

Mac

borg1 · « **Reply #10 on:** January 06, 2005, 10:16:49 AM »

hey folks,

interesting comments!! it seems many of us are on the same page. i do think that when many of us say our guns shoot accurately we mean tight groups. My definition stems from the scientific end, which someone has already pointed out. So if you ever get a chance to mention how 'accurately' your gun shot, please occasionally throw in precise instead, for us anal folk!

A rifle that shoots precise groups, in my book, is the one i want. i can always adjust sights later... hopefully :grin:

jeff223 · « **Reply #11 on:** January 06, 2005, 11:28:50 AM »

if you were to shoot at a coin and you hit it what would you have?
accuracy or precision?i missed the center :oops:

Longcruise · « **Reply #12 on:** January 06, 2005, 01:21:58 PM »

Quote

Precision-Ability to put 5 shots in same hole. Accuracy-Able to shoot 5 shots you can cover with a quarter or dime or whatever

I'd say accuracy = able to hit a quarter or a dime five times consecutively :grin:

Quote

if you were to shoot at a coin and you hit it what would you have?
accuracy or precision?i missed the center

Depends on how many shots it takes to hit it!

MGMorden · « **Reply #13 on:** January 06, 2005, 02:14:55 PM »

If you hit the coin and were aiming at it then that is accuracy. You can never determine precision based on a single shot/measurement. Precision is all about repeatability. If you can repeatedly hit the coin then you have both precision and accuracy. If you hit the coin once and never again then you were accurate once but you are not precise. If you are cosistantly printing 0.5" groups but 10" from the coin then you are precise but not accurate.

Basically when measuring you really need both.

Lets say you're measuring a barrel to determine the exact bore size, and lets say that they actual size is .253", but you don't know that yet. The following two groups of measurements are taken:

Group 1:
.261" .277" .257" .241"

Group 2:
.223" .221" .224" .221"

Group 1 is technically more accurate (every measurement in that group is closer to the real number than the numbers in group 2 are), but the measurements are all over the board. On the other hand, group 2 is precise, being within .002" of every other measurement in the group. The measure is way off though. As you can see, without having both, you're not much good

.

ken s · « **Reply #14 on:** January 06, 2005, 02:39:42 PM »

I think somebuddy's are bored
ken s

:lol: :lol: :lol:

jeff223 · « **Reply #15 on:** January 06, 2005, 02:48:38 PM »

i understand now :wink: good answers :wink:

aulrich · « **Reply #16 on:** January 07, 2005, 05:28:09 AM »

I think we are on the right and I may just have missed it because of language. Wile accuracy and precision are closely related there are not the same. Take a fancy benchrest rig and a regular hunting rifle the benchrest rig on any day is capable of one holers, while the lunch box rig is minute of whitetail (1.5" just to put a number on it).

The bench rest rig is the more accurate by a long shot but the regular gun can be the more precise. This is because between two environmental extremes the one hole groups could be farther than 1.5 " apart. Where the regular rig shoots 1.5 but the point of impact does not shift through the operational extremes.

And when it comes to hunting there no such thing as a sighter shot so precision is more important than accuracy.

gwhilikerz · « **Reply #17 on:** January 07, 2005, 05:35:12 AM »

Depends on what you definition of "IS" is. :grin:

Brett · « **Reply #18 on:** January 07, 2005, 05:37:07 AM »

Is the powder measure half full or half empty :?: :roll:

From Webster's New World Dictionary:

"Accuracy n. The state of being accurate; precision" (emphasis added).

According to Webster's the terms are interchangeable.

superhornet · « **Reply #19 on:** January 07, 2005, 05:55:32 AM »

If one can hit the whitetail using an SB2 30-30 150grain Hornady BTSP over 34.5grains of W748 at 230 yards that is precision accuracy...Brett from the old forum---do you still have that recipe for beaver tail--ho ho ho.

Brett · « **Reply #20 on:** January 07, 2005, 07:16:16 AM »

Quote from: superhornet

...Brett from the old forum---do you still have that recipe for beaver tail--ho ho ho.

I think I might be able to dig it up. Why... has the beaver hunting been good this year. :wink:

MGMorden · « **Reply #21 on:** January 07, 2005, 02:36:09 PM »

Quote from: Brett

Is the powder measure half full or half empty :?: :roll:

From Webster's New World Dictionary:

"Accuracy n. The state of being accurate; precision" (emphasis added).

According to Webster's the terms are interchangeable.

That's the modernly bastardized meaning

. From American Heritage:

pre·ci·sion ( P ) Pronunciation Key (pr-szhn)
n.
1. The state or quality of being precise; exactness.
2.
a. The ability of a measurement to be consistently reproduced.
b. The number of significant digits to which a value has been reliably measured.

ac·cu·ra·cy ( P ) Pronunciation Key (kyr--s)
n.
1. Conformity to fact.
2. Precision; exactness.
3. The ability of a measurement to match the actual value of the quantity being measured.

In common speak they are the same hence the dictionary reference, but in physics and other sciences they are not.

jeff223 · « **Reply #22 on:** January 07, 2005, 02:49:30 PM »

i think you guys have lost me somewhere again :?

MGMorden · « **Reply #23 on:** January 07, 2005, 02:57:13 PM »

Quote from: jeff223

i think you guys have lost me somewhere again :?

Doesn't matter a whole lot. Mostly just a debate of words. It won't matter when you're out shooting. I spent a lot of time having math and science drilled into my head though (computer programmer) which is why I enjoy debating the subject.

Fred M · « **Reply #24 on:** January 07, 2005, 03:20:25 PM »

The subject made me think about an old song. Not fashionable any more.
But here it goes. A pretty little tune with old fashioned lyrics.

Love and marriage go together like a horse and carriage------------.you can't have one without the other.

Does that fit? I htink so.

Lone Star · « **Reply #25 on:** January 07, 2005, 04:20:27 PM »

Quote

The bench rest rig is the more accurate by a long shot but the regular gun can be the more precise. This is because between two environmental extremes the one hole groups could be farther than 1.5 " apart. Where the regular rig shoots 1.5 but the point of impact does not shift through the operational extremes.And when it comes to hunting there no such thing as a sighter shot so precision is more important than accuracy.

Nope, ya got it backwards - accuracy is more important for hunting big game. Accuracy = hitting what you aim at. Precision = small groups.

The benchrest boys have two different kinds of competition, one measures precision and the other measures accuracy. Aggregate Benchrest is the most well known, and that is where those tiny 0.10" bragging groups come from. Small groups is where it's at here, and the group can be anywhere on the target paper.

Hunter's Benchrest is a measure of accuracy. The shooter has a target with ten small bullseyes on it, each with scoring rings. He takes one shot at each bull and then adds up the total score. A score of 100 means he hit the ten ring all ten times he shot - great accuracy, he hit what he aimed at. No groups to measure either, as group size doesn't matter.

The precision shooter could have missed the deer, putting all his shots into a nearby tree trunk. The accurate shooter hit the deer - where he aimed.

Brett · « **Reply #26 on:** January 07, 2005, 05:08:06 PM »

Lone Star you win the prize in my judgment. You have shown us the best example of precession vs accuracy. My hat is off to you. :agree:

Fred M · « **Reply #27 on:** January 07, 2005, 05:33:04 PM »

Lone Star.

The tiny 1/10 groups come from precision rifles and ammo.

The accuracy needed to hit 25 x's in a Hunter match requires the same precision. of equipment.

So I still say you can't have one without the other.

But your point is well taken, it is a good analogy. I also buy the Websters dictionary explanation. Accuracy and precision being the same.

Isn't that a brain twister? It comes down to the application.

MGMorden · « **Reply #28 on:** January 07, 2005, 06:58:40 PM »

Quote from: Fred M

Lone Star.

The tiny 1/10 groups come from precision rifles and ammo.

The accuracy needed to hit 25 x's in a Hunter match requires the same precision. of equipment.

Actually it doesn't require the same precision. The rifle shooting for X's might be fine with 0.25" groups. That's not the same level of precision as the rifle shooting 0.10" groups. However, if the rifle shooting 0.25" groups hits on average 0.3" from point of aim and the rifle shooting 0.10" groups is hitting 5" from point of aim, then the 0.25" group rifle is more accurate, despite the fact that the other rifle is more precise. The some degree it's splitting hairs, but there is a difference.

As to having one without the other, it's not possible to get consistent accuracy without precision, but when we bring consistency into the talk then we've really shifted discussion to precision anyways. You can definately have precision without accuracy though. If your scope is off for example. Sure your rifle might be the straighest shooting thing on the block, and it might be able to shoot 3 shots into the same hole at 100 yards. If the scope is off and you take a shot at a deer though, you might very well miss because the scope was not set and though precise, it is no longer accurate.

Badnews Bob · « **Reply #29 on:** January 07, 2005, 07:13:17 PM »

Hey Jeff I'm not lost with this..... I know exactally where I aint! :-D