How Accurate is "Accurate"

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  • Last Post 16 October 2014
John Alexander posted this 11 October 2014 

          I was questioned recently about what I meant when I said something was accurate. What did I mean by “accurate?” Fair enough.  I often have the same question about others' posts and wished they would be more specific.

    Everybody on this forum is interested in being able to consistently hit something with his cast bullets.  It may be a bean can at 20yards, the right spot on a moose at 100 yards, a squirrel's head at 50 yards, or the ten ring on a CBA target at 200 yards.  One sport's accurate rifle is a piece of junk for another sport.  Maybe we should suggest a set of definitions of “accuracy” as guidelines for posts on this forum.  Nothing required of course but just some suggestions about how to speak of accuracy to sharpen up our posts.     For starters, we all know that quoting the size of the best group in a shooting session, or the size of groups “except for the fliers” is misleading and a waste of ink -- at best.  Maybe we could agree that when we speak of accuracy we are talking about some kind of average accuracy for all the shots, not about the “wallet groups."   What suggestions do you have?   John

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onondaga posted this 11 October 2014

http://www.castbulletassoc.org/view_user.php?id=6375>John Alexander

I consider 10 Shot Groups  of 1” or under at 50 Yards accurate for small game and big game hunting with cast bullets. Any rifle that I cannot get to perform that well is sold or traded off. Every rifle I have will do that well or better with at least one practical  hunting load that the rifle was purchased for.

Gary

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Bud Hyett posted this 11 October 2014

The terms “precision” and “accuracy” in a statistical sense are often confused. Not wanting to get into an endless argument, I'll try to explain. The precision of a rifle and load are the ability to put a bullet on a target; the accuracy of a rifle is the ability to repeatedly group bullets within the area of that target. I've spent many hours at lunch breaks arguing with a fellow shooter who is a statistician about these terms.

"Precision” refers to the ability of the rifle or pistol to place a bullet within a designated area on a target.

"Accuracy” refers to the probability of this happening, i.e., repeatability of the groups shot.

When I state that a rifle and load is “accurate” enough to make a shot at 100 yards, I am really stating the rifle  and load has the precision to be capable of a hit.

When I state I can do this shot every time, I am stating the rifle groups well enough, i.e., “accurate", to hit a target in the stated condition.

When I state I have a rifle capable of hitting prairie dogs at 500 yards, that refers to the precision of the rifle and the capability of the nut behind the rifle butt. 

When I state I have a rifle accurate enough to be sub-minute, this means the rifle will group ten shots within one inch at 100 yards nineteen out of twenty groups.

This is my personal standard and I own a few rifles and long-range handguns that will make the standard.

I love the Ruger #1 and own six of them, they are equally divided for the sub-minute category. Three are sub-minute rifles and three do not make the grade.

What I expect for the accuracy of each is within the following range: .218 Bee - .600; .22-250 - .900, .220 Swift - .900; .22 Hornet - 1.000, 6mm Remington - 1.100; .30-'06 - 1.250. This is for ten-shot groups at 100 yards. These are the repeatable groups, they sometimes shoot better.

In a strict definition, shooters use the term “Accuracy” to also cover the term “Precision"; but this usage is understood and the communication is passed. I think the term “accuracy” is well understood to cover both instantiations outside of a technical journal.

Farm boy from Illinois, living in the magical Pacific Northwest

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frnkeore posted this 11 October 2014

This is what my definition would be like for longer string match shooting (aggregate). I would look at it the same as standard deviation as say that 1” at 100 yards, 80% of the time and 2.5” at 200. Both for 10 shot groups.

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tlkeizer posted this 11 October 2014

Greetings, John, I consider accurate as one shot one caribou, one shot one moose, one shot one deer,none traveling over 80 yards from reception of bullet, 10 shots with minimum 9 prairie dogs out to 250 yards, none traveling more than distance back to the ground.  HOWEVER, I do like to try for repeated accuracy on paper as 3,5, or 10 shot groups covered by as small a circle as can be repeated on demand.  Going down the bunny trail of one shot, for one shot, I kind of prefer jack daniels at the end of the day beside the fireplace before heading to dreamland. TK

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OU812 posted this 11 October 2014

Accurate is a gun that groups well from a clean cold barrel and groups do not wander when barrel heats up and starts to foul.

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RicinYakima posted this 11 October 2014

I suppose that I did not learn my lesson the last time the board had this discussion of words and their meanings.

Accuracy: The ability of a rifle and ammunition combination that will place all (choice a number) of its bullets within a defined area ( 1 inch, etc.) at a proscribed distance. (Mine is 10 shots within the 10 ring of the CBA Military Rifle target at 100 yards.)

Precision: The ability of a shooter to place the bullet from the one cartridge in the barrel at a precise point upon firing.

FWIW, Ric

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John Alexander posted this 12 October 2014

BHyett wrote: In a strict definition, shooters use the term “Accuracy” to also cover the term “Precision"; but this usage is understood and the communication is passed. I think the term “accuracy” is well understood to cover both instantiations outside of a technical journal. Good point BHyett.

In any discussion there is often someone reciting the difference between accuracy and precision as he understands it.

In the English language (unlike French) usage governs.  So if the term “accuracy” is used commonly to cover both concepts and is used long enough then it becomes correct usage.

Let's stop worrying about it.

John

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Wineman posted this 12 October 2014

When I took Quantitative Analysis (numbers class for Chemistry) The intro to the Textbook showed an archery target to explain the relationship between accuracy and precision. Precision was three arrows in the 8 ring all touching. Accuracy was three arrows loosely grouped around the Bulls eye and Accuracy and Precision was three arrows touching in the Bulls-eye. That has always stuck with me.

Dave

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Ken Campbell Iowa posted this 13 October 2014

  • accuracy * is not a precise term.
  • precision * is not an accurate description of how guns shoot.

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John Alexander posted this 13 October 2014

I think most shooters understand the difference between “accuracy” and “precision” as defined by statisticians or they should be able to understand it with a statistics book or better yet with the posts by BHyett, Ric, and especially with the help of the great image provided by Wineman.

Of course statisticians need to use the terms  the way statisticians define them to communication with other statisticians.  It gives them the vapors and they are in danger of falling over in a dead faint to hear shooters use the term accuracy to cover both concepts.

However that's the way shooters have been using the term accuracy for at least the 70 years I have been paying attention and if you want to communicate with other shooters I believe it is the correct term for the way we have been using it.

We have a similar situation with the term “headspace” where shooters have been using it wrong (according to the SAAMI definitions) forever. (We had a useless argument about it in a thread long ago and far away on this very forum.)  But if you want readers in a shooting article to understand what you are saying you should use the term “excessive headspace” as the readers understand it.

Writing down the definition of an English word in a statistics book or a SAAMI publication, or a dictionary for that matter doesn't mean that it stays the same forever or that it has the same meaning for different professions.  There are many examples (Think of the term engineer). That's why English dictionaries change the definations of words over time.

These arguments about the misuse of “accuracy” or “headspace” by shooters reminds me of something Churchill is supposed to have written back to an overly pedantic reader who had corrected him for ending a sentence with a preposition.  "This is the type of bloody nonsense up with which I will not put." 

I feel the same way about accuracy and precision.

John 

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joeb33050 posted this 13 October 2014

John Alexander wrote: I think most shooters understand the difference between “accuracy” and “precision” as defined by statisticians or they should be able to understand it with a statistics book or better yet with the posts by BHyett, Ric, and especially with the help of the great image provided by Wineman.

Of course statisticians need to use the terms  the way statisticians define them to communication with other statisticians.  It gives them the vapors and they are in danger of falling over in a dead faint to hear shooters use the term accuracy to cover both concepts.

However that's the way shooters have been using the term accuracy for at least the 70 years I have been paying attention and if you want to communicate with other shooters I believe it is the correct term for the way we have been using it.

We have a similar situation with the term “headspace” where shooters have been using it wrong (according to the SAAMI definitions) forever. (We had a useless argument about it in a thread long ago and far away on this very forum.)  But if you want readers in a shooting article to understand what you are saying you should use the term “excessive headspace” as the readers understand it.

Writing down the definition of an English word in a statistics book or a SAAMI publication, or a dictionary for that matter doesn't mean that it stays the same forever or that it has the same meaning for different professions.  There are many examples (Think of the term engineer). That's why English dictionaries change the definations of words over time.

These arguments about the misuse of “accuracy” or “headspace” by shooters reminds me of something Churchill is supposed to have written back to an overly pedantic reader who had corrected him for ending a sentence with a preposition.  "This is the type of bloody nonsense up with which I will not put." 

I feel the same way about accuracy and precision.

John Oh yeah? Let's say you had a pin, and the pin had a head. Just exactly how many angels could dance on it. Waltz? Hully-gully?, Jitterbug? Big angels? Cherubs? What does SAAMI have to say?

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James S posted this 13 October 2014

I've always looked at accuracy and precision from a quality control point.  Most likely due to my training in R&D.

Accuracy of a tool is the degree of closeness of measurement to the actual value. The precision of same tool is its ability to repeat the same results under the same conditions. So the accuracy of my firearm is the closeness of point of contact to point of aim.  And its precision would be its ability to hit that same point every time.

If I bolt the firearm in a 'proven' rail mount and I aim it at the 'X' but it hits every time up and over in the same spot, I have a very precise inaccurate firearm.  So I adjust my sights and have both!   But if my firearm is not precise I got no ability to test accuracy and I must gauge my accuracy within the limits of my precision.  I now must say it can hit the 'X' within the limits of 1 moa at 100 yards etc.  We loose the significance of accuracy within the precision error of the system(firearm). And we haven't even started on my ability to aim accurate precisely.  Or load the round precisely, and read the wind, and maintain the firearm.  Any of which will screw with the accuracy and precision because now I'm an integral piece of the system.   It's just easier to reduce the precision to the lowest error by the usual methods of barrel replacement, bedding, trigger adjustment and sight installation or upgrades and then adjust the point of aim and if it ain't good enough sell to whoever thinks its good enough for them.

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tturner53 posted this 14 October 2014

To me they both mean the ability to put a bullet center of mass on demand at the intended range of use. All else is entertainment. Maybe my standards are low.

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Chargar posted this 14 October 2014

These terms are both subjective and contextual. Any attempts to standardize them is an exercise in doing vain things.

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joeb33050 posted this 14 October 2014

Chargar wrote: These terms are both subjective and contextual. Any attempts to standardize them is an exercise in doing vain things. Well, maybe not. Lexicographers write down the meanings that people assign to words, many times more than one meaning per word. What is going on here is the thirteenth annual argument about the meanings of two words. Some folks demand that THEIRS is the correct meaning, others disagree. Stop the nonsense and write down the several meanings of each word-go to the printed word for these meanings. “He wrote it, I understand what he wrote” is the test.Saying that the round thing in your car that you hold onto and turn whilst driving is an ACCELERAIOR is true, but true ain't what language is about. Language is about conveying and recording meaning.You're so vain, I'll bet you think this post is about you!   

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John Alexander posted this 14 October 2014 

   I started this thread in an attempt to see if we could agree on some more of less standard or guideline that defines what we mean when we refer to how “accurate” a rifle, load or combination of rifle, shooter, and load is.

   I suppose I should have anticipated that things would degenerate down to a rerun of the great accuracy vs. precision rant. I had hoped we could avoid that exercise in semantics because shooters almost universally use the term accuracy to describe both terms as statisticians define them.  I thought we could communicate just fine without that fine distinction since most of us aren't statisticians. I am sorry that my initial post wasn't clear and I got us into that tangle -- again.   What I had in mind for example was a guideline perhaps similar to the standard used by the Am. Rifleman's technical staff. They use the average of 5 five-shot groups.  The results defines how “accurate” the gun being tested is as far as the Am. Rifleman is concerned.  There is nothing special about 5-five shot groups but it is simple, doesn't take too long, and it gives the reader a pretty good idea of what the results mean and if the test were repeated the results wouldn't be too radically different -- most of the time.  Note that they call it “accuracy results.”    The way things are now when a poster says the (load, rifle, pistol. etc.) will group 1.5 inches at 100 yards we have no idea whether that is once in an afternoon, once in year, most of the time if you disregard the fliers, an average of several groups of _ shots each, or that it will do 1.5 inch or smaller with 95% confidence.  Often the post also doesn't tell the reader whether 3, 5, 10, or 20 shots went into the 1.5 inches.    My personal suggestion for a guideline is the reader could expect that a statement about accuracy would based on a minimum of twenty shots shot fired consecutively with no shots disregarded.  The results could be quoted as 7 3-shot groups, 4 5-shot groups, 2 10- shot groups, or 1 20-shot group. It wouldn't make much difference what size of group was used since the size of groups of one number of shots can easily be converted to the equivalent of a group of some other number of shots by reading Joe's book.   Of course, if we did agree on some sort of minimum suggestion, it would only be a voluntary guideline and posters would be free to ignore it and report accuracy in any cryptic way they wished.   John

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James S posted this 16 October 2014

If I get Johns point...Accuracy reporting has a lot that needs to be clarified. A load maybe set up for an accurate shot in a light weight barrel in the high mountains on a cold day. Or you have a bull barrel that can take 10 shot groups all day long. To understand a firearms accuracy a reader needs the facts. But there are so many.

We would need temp, weather, firearm make, load, design limitations, number of groups and number of shots per group. Maybe even at what point the firearm exceeds the design parameters or becomes inaccurate. I would not be able to convert all those and maybe many more I left out, to a standard reporting format. Like say an average temp of 72 deg, with a humidity of 33%, under fair sky's, at sea level. With a barrel of 24 oz bedded in a synthetic sportier mount.

For example reporting 5 groups of 5 on a hot day with a light weight hunting rifle would show a poor performer while 8 groups of 3 shots on a cool day with cool down periods would show it an excellent performer.

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joeb33050 posted this 16 October 2014

James S wrote: If I get Johns point...Accuracy reporting has a lot that needs to be clarified. A load maybe set up for an accurate shot in a light weight barrel in the high mountains on a cold day. Or you have a bull barrel that can take 10 shot groups all day long. To understand a firearms accuracy a reader needs the facts. But there are so many.

We would need temp, weather, firearm make, load, design limitations, number of groups and number of shots per group. Maybe even at what point the firearm exceeds the design parameters or becomes inaccurate. I would not be able to convert all those and maybe many more I left out, to a standard reporting format. Like say an average temp of 72 deg, with a humidity of 33%, under fair sky's, at sea level. With a barrel of 24 oz bedded in a synthetic sportier mount.

For example reporting 5 groups of 5 on a hot day with a light weight hunting rifle would show a poor performer while 8 groups of 3 shots on a cool day with cool down periods would show it an excellent performer.I don't think so. The measure of accuracy that I use is average 100 yard group size for five groups of five shots shot at the same sitting. On one day at the range. Temperature, wind, hurricanes, mood swings, medication, diet-none are included.What is included in the record is gun, scope, powder, charge, primer, bullet, size, lube and anything else you consider worth recording. But it doesn't matter.In developing a load, once you've found a suspect, do it again. Another 5 shot five group 100 yard average. When the averages don't vary much over a few tests, you can start to make meaningful statements. An example: For seven sets of five five shot 100 yard groups = 35 groups  the average group size was 1.196", five group averages ranged from .995” to 1.495, group size varied from .700” to 2.275".This is what I think is needed to understand what accuracy is, a lotta shots on a lotta days with pretty much the same bun/ammunition/shooter.We need better agreement about the number of shots/groups/range days are required to make accuracy statements. Not what's RIGHT or TRUE, just what's agreed.Meanwhile, let me show you this group I've got in my wallet! 

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