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TTAG Commentator Dyspeptic Gunsmith [not shown] writes:

OK, let’s clear up some misconceptions:

1. Very good accuracy in a 1911 would be a 2″- group at 25 yards from a rest. Exceptional accuracy for a semi-auto pistol is a five-shot group of 2″ at 50 yards. That’s what the S&W Model 52 used to be tested to achieve. The S&W 52 would also be expected to put “10 rounds in the 10″ at 50 yards, a target area of about 3.3”. The S&W Model 52 was the pistol of the USAMU for years in the 60’s and 70’s.

Ransom rest (courtesy ransomrest.com)

2. Pistol accuracy is measured from the pistol being held in a Ransom Rest. Not shooting offhand, not shooting off sandbags, not handing it to a champion bullseye shooter.

3. A full length guide rod on a 1911 is a “solution in search of a problem.” Yes, I know all the supposed benefits of a full length guide rod. Want to know how many springs I’ve seen kink with a standard guide? None. I’ve fixed a bunch of 1911 issues for customers, and never has even one customer come to me with an issue that would be fixed with a full length guide rod.

4. Once the CNC machine mills the parts to exacting tolerances (and might I say these tolerances can only be achieved with a machine,)…

This will come as news to many gunsmiths, especially those who are old enough to remember match pistols from the “BC” (Before CNC) era of gun production. I regularly fit up parts with nothing more than files, polishing paper, lapping compound, measurement tools, a smoke lamp and a granite reference plate to tolerances tighter than the typical CNC machine can achieve.

The TIR on most CNC spindles is 0.0002″, the typical repeatable positioning accuracy is 0.0002″, even if you can command the machine to 0.0001″. OK, if the manufacture is running a machine like a Kitamura MyCenter, now we’re talking a temperature-controlled machine that can position down to 78 millionths and repeat down to 39 millionths of an inch.

Hand fitting with a smoke lamp and abrasives can get you down to a tenth or less. It just takes time, and skilled time costs money.

5. Let’s talk about accuracy – what is accuracy?

Accuracy is repeatability. Lots of people conflate or confuse accuracy and precision. They’re two very different mathematical ideas.

Precision is how tightly you can describe a measurement or observation. In a gun, let’s say you have a 40X March benchrest scope on a hunting rifle. You take your rifle on to the range at 100 yards. You not only see your target card in glorious detail, you can see a fly taking a crap on your target. With a 40X magnification scope, you could probably see a .223 hole in a target at 300+ yards, if the conditions are OK (ie, low heat shimmer).

What you have here is a very high level of precision – you can resolve individual holes in the target, you can even see a fly land on your target at 100 yards. If we want a different example, let’s say you have a measurement instrument (eg, a set of digital calipers), and thanks to the magic of digital electronics, you might have precision down to 0.0001″.

Now let’s talk about accuracy. Accuracy is how well you can repeat your shots. With your hideously expensive, but very nice, March scope, let’s say you send a round downrange. You can see your hole at 100 yards from a .223 round without a spotting scope. Your oh-so-wonderful scope allows you to see exactly where you put your first shot.

Now you want to shoot for a group – so you lay the crosshairs over your first round’s hole. You send the next one downrange… and it lands to the right and slightly up by about 1.5″. You can see quite clearly the first hole in your target, and now you can see the second hole in the target.

How accurate is your rifle at this point? Not all that much. You send down four more rounds while laying the crosshairs on your first bullet’s hole. You look at the group – eh, about 2″ for the most extreme spread, center-to-center. That’s mediocre accuracy. But man oh man, you’ve got precision coming out your ears – accuracy, not as much.

Accuracy is how well you can repeat something. Let’s go back to the set of digital calipers – they resolve or have precision down to 0.0001″. What’s the accuracy of that measurement instrument? About the same as for any other set of calipers – +/- about 0.002″ – and order of magnitude worse than the precision.

Same deal with a gun – if it can’t lay the rounds in one on top of the other, even when you can see exactly where the bullets are going, you’ve got an inaccurate gun with great sights.

When I’m shooting my Anschuetz rifle with match ammo, at 50 feet, if I can’t put every bullet in the center ring on an indoor offhand target, it’s my fault, and never anything but my fault. The rifle, sights and ammo are of such accuracy, that there’s no excuse on my part – even tho I cannot see the center ring in the aperture sights at 50 feet.

RELATED ARTICLESMORE FROM AUTHOR

80 COMMENTS

  1. “so you lay the crosshairs over your first round’s hole.”

    WHY?????
    It dilutes the results to do that.
    You should have your crosshairs on the same spot for each spot, no?

    • Let’s say that you’re using an imperfect target – or even a perfectly blank piece of paper.

      Many times when I’m testing a rifle for accuracy, I’ll throw up a blank piece of butcher paper. I’ll throw one round downrange for my fouling shot, then put the crosshairs on that first hole and send another five to see what we’ve got.

      It’s cheaper than buying targets, and I’m going to have to shoot at least one fouling shot anyway…

  2. In not so many words, Precision is what you can measure accuracy is how well you do it.

    Excellent article, as said even with the advent of super precision CNC everything hand fitting is not dead by any means.

    It is nice to see a distinction between practical accuracy and “engineering” accuracy (holding it in a rest.)

    • It will be soon enough if the ITAR regs go into effect that will deem any such activities “manufacturing.” (See posting from yesterday.) The best will survive, because the best probably get paid the most, and will be able to afford the exorbitant extortion to register with the Dept. of State.

      • The upshot of the ITAR issue is this:

        It’s another cost that has to be passed on to the customer. If my power utility raised my power rates to $1.00/kWh in order to have power generated by unicorn flatulence and Smurf berries, well, I have to pass that along to my customers as an increased cost.

        Now, if the customers do not want to pay the increased price, well then, that’s bad for me.

        My wife and I are debating how we’re going to break it out on the invoices, and what we’re going to call it. If we call it out as ITAR, then I’m going to have to write up something to attach to the invoice to explain what ITAR is, and how this was foisted upon us, so I don’t have to get into a half-hour explanation with each customer why there’s a (eg) $40 fee on their invoice for ITAR.

        • An Oburden charge?
          Government mandated license fee?

          The “If you like your Gunsmith you can keep your Gunsmith” adminstrative surcharge pass-through?

        • I really have no firm idea yet. Every business has input and regulation costs they pass on to consumers, but this one is different than most that apply to the gun industry. It’s not a “ongoing” or “per piece” expense. It’s this absurdly high annual “fee” for the privilege of being caught in the goofy and commie agenda of the US State Department. The FFL costs are trivial – I just renewed for $90 plus postage. That comes out to chump change in the term of the FFL.

          But more than $2K/year? OK, this is getting annoying.

          If you thread/chamber/profile lots of barrels per year, you can spread this out among lots of customers. You either raise your hourly rates, or you add a per-job charge. We’re thinking about a per-job charge, because the classification of manufacture is being laid upon mostly those jobs that require precision machining (chambering/threading/profiling barrels, building custom guns etc). Changing parts, cleaning, etc – that’s not part of their agenda. I think it is important for more people to see this nonsense show up where they can see it – so I’m inclined to put “ITAR fee” on the invoice, with some reasonable amount that reflects my estimate of how many customers’ jobs will fall under the State Dep’t definition of manufacturing per year and how I spread this new expense over that customer base.

          If a ‘smith doesn’t have a large number of customers, they have a problem – you can’t whack one customer with the whole fee, that’s absurd. Likewise, you can’t hit 10 customers each with 1/10th of the fee.

          We already have two different shop rates – one for benchwork ($65/hour) and one for machine work ($75/hour) to reflect the cost of tooling consumables for machining, with some operations being so common that they have a set price (eg, muzzle threading for putting a can on AR barrels is becoming rather popular here).

  3. “Pistol accuracy is measured from the pistol being held in a Ransom Rest”

    This is measuring the precision of the gun/cartridge combo, not accuracy.

    • No, again, you’ve conflated the two.

      When you put a pistol in a rest, and you fire the pistol at the same point of aim at 25 or 50 yards, you’re now testing the repeatability (accuracy) of the pistol (and ammo) alone. You’ve taken the human component out. Accuracy is what the instrument or firearm, alone and all by itself, can repeat. The precision of the pistol is what you have in the sights, which for most iron pistol sights isn’t much, so you’re typically adjusting the sights so that you’re holding a 6-o-clock on a black bullseye target.

      Let me expand on my other example, the digital calipers issue: I see kids running around machine shops all the time now with their new-fangled digital IP67 calipers. Oh, they’re so pleased with themselves. They think they don’t need vernier micrometers at all any more, those digital calipers are just so special.

      Then I grab a gage block and show the kids how poorly their calipers repeat the same measurement, on the exact same gage block. Typically, the youngsters with over-eager thumbs and little attention to detail can’t get a set of digital calipers to repeat to within 0.002, despite the fancy digital reading being down to 0.0001. That’s because on ANY set of calipers, if you thumb the jaws together hard enough, you can warp the bar between the jaws and cause jaw flex – which gives you +/- 0.002 (or worse) accuracy on the instrument, regardless of how precisely the digital readout allows you to read your measurement.

      So how much more accurate are digital calipers than old-fashined dial or vernier calipers? NONE. They all have the same inherent limitations of design, and the actual mechanical design of calipers hasn’t changed a jot since Mauser (the German gun company) came up with the multi-function (inside/outside/depth) style of caliper in the 1920’s. Putting a digital readout on calipers is exactly the same thing as putting a March 40X scope (which are exquisite pieces of glass) on a Mosin. The glass doesn’t make the Mosin any more accurate – it is what it is. The March scope just allows you to see for yourself by how much you missed your point of aim – and that’s precision.

        • So a precise gun is one with a small group; an accurate gun is one where the group centers around the point of aim. Not forgetting that these are independent; you can have a 24″ group at 25 yards, but still be accurate, if you average all of the relative coordinates and it ends up being on the point of aim. You can have a .5″ group at 1000 yards, but it would not be accurate if you were aiming at the bullseye but you hit the target of the guy 3 lanes down. Plus that guy is going to be a combination of confused and upset at you. 🙂

    • If that pistol/cartridge combo make one ragged hole, it’s accurate. If it scatters holes with a spread of several inches, it’s not accurate.

      One thing DG didn’t come out and say is that you can’t have accuracy without precision. You won’t get accuracy out of a laser beam if you don’t have a precise way to aim it. That’s why they sell scopes.

      The purpose of the random rest is to allow precise aiming, such that you can measure the gun’s accuracy without introducing other uncontrolled variables.

        • The problem with the definitions in the link you posted, useful as they might be within the realm of scientific measurements, is that they are useless in estimating the probability of whether or not I can kill a deer from 300 yards. For that, I need repeatable performance, which is what we refer to as accuracy in the world of ballistics.

        • Curtis, you and DaveR are saying the same thing. In hunting accuracy (i.e. Bullet goes to point of aim) is the most important factor. The vital zone on a deer is 8-10 inches, so at 300yds a rifle capable of 2.5-3 MOA of precision is more than adequate. However, you need to have nearly perfect accuracy or shots will impact off the target. If you cannot repeatably place shots at your desired point of aim (accuracy) then you increase the probability of a miss.

          This can be overcome to a certain degree with an increase in precision. With a rifle capable of .5MOA of precision, at 300yds your point of impact can deviate from your point of aim by almost 4 inches and still have a reasonable chance of hitting vitals on a deer sized target assuming in all cases you are aiming for the perfect geometric center of the vital zone.

  4. As a statistician, I approve of this explanation of accuracy vs precision. Lots of people say one when they mean the other. As usual, excellent and informative stuff from DG.

    • “As a statistician, I approve of this explanation of accuracy vs precision”

      Not sure what type of statistics you have been trained in, but this article is quite wrong. Precision in science and statistics is defined as the repeatability of a measurement (DP calls this accuracy). Accuracy OTOH is the closeness of a measurement to the real value. It’s actually pretty simple.

      • Repeatability of a measurement is different than the repeatability of separate measurements.

        He used the claliper example to explain this. Take your calipers and measure the length of the same cartridge five times. It won’t always be the same.

        • Yeah, his caliper example is wrong too.

          The precision of the calipers is defined by how repeatable they are in the measurements of a something.He’s confusing the resolution of the calipers (0.0001″ or whatever) with their precision (that’s the +/- factor that is always reported)

          The accuracy of those calipers (or of a precision balance) is how close those measurements are to what the true measurement is.

      • Accuracy in a gun is the same thing: how closely do your shots come to your actual point of aim? If you have a scope that allows you to very precisely choose your point of aim, and your shots don’t hit it, you have precision (the ability to finely measure your point of aim) without accuracy (the ability to actually hit your point of aim).

      • Precision, when I worked in an electrical engineering lab calibrating lab instruments to NIST (back then, NBS) standards, was how finely I could make a reading. eg, Some voltmeters at the beginning of the digital instrument revolution could read down to microvolts.

        Accuracy of the instrument was whether or not the instrument’s reading reflected the actual NIST voltage standard. A voltmeter out of calibration could still read down to milli or micro volts, but it would be biased off the actual voltage – or what we called “precisely wrong.”

        • Holy cow, did you ever stir up the troll nest! So many attacks tells me you must be correct, regardless of anything else(like that you actually are).

        • I could well be wrong, since I was taught my definitions back when programmable calculators were the hot new (and unaffordable) thing to have in engineering schools, we still used the word “decimate” to mean “reduce by one-tenth” instead of “totally destroyed,” we used a comma before “and” without calling it “Oxford,” and no one gave a rat’s rear end “how mathematics made us feel…”.

        • Its really all semantics anyway. Wikipedia calls precision the degree to which repeated measurements under unchanged conditions show the same results. But accuracy has many different meanings depending upon the usage. Some say tomato and some say tamaato, but in Montana, and I suspect Wyoming also, Its always tomato.
          In the context of firearms, I have always used the meanings exactly as you said in the article.
          I really want to vent here over the ITAR issue but its hard on my blood pressure so I wont. I’m one of the small shops that only chambers and threads barrels a few times a year, and mostly just fixes broken or sprung parts issues. I am between a rock and a hard place here. I’m leaning towards just putting up a sign that all rebarrel jobs must be pre threaded/chambered from now on. The bulk of my machining here in a small town is on farm equipment anyway. But it sure is frustrating that I soon wont be able to do what Ive been doing for 30 years now without a huge fee to some burrocrat who doesn’t know the difference between a fly cutter and a pair of pliers…

        • To DG: your point on “decimate” is a pet peeve of mine. I’m glad to hear someone else understands that the prefix means 10.

          Ignorant, not-so-intelligent writers these days use “decimate” thinking they are saying “obliterate” or “soundly defeat”, but what they are really saying is “inflict 10% casualties or fatalities”.

      • Biostatistics. And I reread the article and my stats textbook definition, and have to retract my statement. As others have said, your rifle is accurate if your shots are centered around where you aim it. It is precise if you get a tight group. The two are independent, so you can be accurate but imprecise or vice versa.

        Guess I unwittingly proved my own point about people confusing the two!

    • Biostatistics. And I reread the article and my stats textbook definition, and have to retract my statement. As others have said, your rifle is accurate if your shots are centered around where you aim it. It is precise if you get a tight group. The two are independent, so you can be accurate but imprecise or vice versa.

      Guess I unwittingly proved my own point about people confusing the two!

  5. This is the worst article I have ever read on discribing accuracy vs precision. At no point in your rambling, incoherent response were you even close to anything that could be considered a rational thought. Everyone in this room is now dumber for having listened to it. I award you no points, and may God have mercy on your soul.

    • Let me simplify it for you: Precision is what you get from a machine (or an incredibly skilled craftsman with a lot of time on his hands and a customer with deep pockets). Accuracy is what you get from humans.

      On the other hand, humans built those damned machines. The real question is how much precision is really necessary and how much accuracy is sufficient for the task at hand?

      So, precision is an expensive Swiss watch. Accuracy is a Timex or a Swatch. Aside from the price, what is the real-world difference?

      • I will take the time piece question.

        In the real world to get to work, it does not matter as long as you there in relative time.
        If you are in some type of competition be it automotive sports or track and field, it does matter considering sometimes winning is a matter of tenths or hundredths or thousands of a second.

        Same goes for guns, accuracy is good enough for defense or for plinking in the back yard against soda cans.
        However, in benchrest competition where the number of X’s you can get can mean the difference between win or a loss it matters.

  6. Great article, sir. Although I might add that aiming at the first hole through the 40X scope could be counterproductive if the rifle / load combo is not perfectly sighted in. As in, chasing the zero. I’m sure you’re aware of that, but readers may not be.

    Also it seems to me that exceptional accuracy isn’t possible without first achieving a very high degree of mechanical precision. I’ve heard lots about 1/2″ groups from off the shelf cheap rifles shooting crap ammo, I just haven’t seen it in the field. Not ever from a 5 shot group. Again, something I’m sure you are intimately aware of with your knowledge of F class and such, but more for the benefit of other commenters.

    There’s also the benefit of having a very wise gunsmith diagnose what the issues are within a current ammo / rifle / optic / mount / (shooter) / environmental combination. I suppose broadcasting your details might give you more work than time that you have available, which is a shame because I could use the skills of an exceptionally good gunsmith where I lives behind enemy lines.

    I appreciate your technical details and wish that I could use your services, particularly when it came to diagnosing some of the accuracy issues with my Savage 110BA / Bushnell ERS / La Rue LT 111 / Ken Farrell 20 MOA rail combo, since I’m still slogging through it on my own. Right now that gun is shooting an “honest” 1.5 MOA through 3 different loads. Not very impressive. So the process of diagnosing, and saving up for better ammo, continues. It’s probably the ammo, but we’ll see.

    I can happily report that every firearm in my collection is now mechanically reliable (other than my worn out Glock 27). I can’t afford ultimate accuracy, so maybe I should change my name. Instead, I’ve gone more towards the prepping route.

    Anyways, another great article from DG.

    • Dyspeptic is an old-fashioned word not often used anymore. It describes someone who is irritable due to depression or indigestion. Yep.

  9. This book explains it . if you like to read technical stuff Modern Advancements in Long Range Shooting, Brian Litz he goes into detail about the difference between accuracy and precision.

  10. My attempt at an analogy to shooting: Precision is a tight group. Accuracy is how close you hit when aiming for the bulls-eye. You can have both or neither.

    Here is how I heard it described when I was in “Colege”:
    Accuracy refers to the closeness of a measured value to a standard or known value.
    Precision refers to the closeness of two or more measurements to each other.

    Dyspeptic got both of these in the comments. I liked the story myself.

  12. To complicate matters on the Ransom Rest – it’s fine for revolvers, but in actuality a human shooter can get more accurate results from aiming a semi-auto pistol, than a Ransom Rest would deliver.

    The Ransom holds the frame in rigid position, returning the frame to the exact same point shot-after-shot. For a gun whose barrel and muzzle are intrinsically linked to the frame (such as a revolver), that works great, and it does effectively return the gun to the same precise point of aim, every single shot. But for a gun with a moving slide, it doesn’t necessarily return the gun to point of aim!

    Try this experiment – safety-check your gun, then grab the slide and move it side-to-side. If there’s any flex at all, then that’s an indication that your pistol may not do so well on a Ransom Rest. A super-tight-tolerance 1911 might do great, but your typical Glock won’t. It’s not uncommon to see a Glock deliver a 4″ or even 6″ group at 25 yards from a Ransom Rest, whereas when a human fires it, it might deliver a 3″ or 4″ group.

    Why? Because the human re-aims between every shot, and aims based on the sights, which are affixed to the slide, so if the slide doesn’t return to the absolute exact same position shot after shot, that’s okay — the human compensates for that. The Ransom rest doesn’t. It returns the frame to the exact same position, but doesn’t account for variations in the slide position.

    This is the same reason a frame-mounted laser is of limited use for distance shooting with a semi-auto handgun. If it’s mounted to the frame, it’s not going to take into account any positional variance of when the slide cycles. A slide-mounted laser (or red dot) would lend to more real-world accuracy than a frame-mounted laser, as it would be a better indication of the true point of aim.

  13. Technically you’re conflating as well. What you describe is the repeatability of a gun, not its accuracy.

    Accuracy is the sum total of all measurement errors when compared to the “true” value.

    In gun terms, the accuracy is the ability of a gun to put the lead exactly where you want it.

    So let’s take it out…

    Resolution / Precision is how well you can aim the bullet. This is going to be solely determined by the quality of our eyes / sights / optics.

    Repeatability is how consistently your gun throws the lead. Not relative to where you aim, but relative to where your shots land. (i.o.w. your “spread”)

    Accuracy is the mean deviation of your shot from the point of aim.

    • OK, I’ll buy that, if we want to introduce ‘resolution’ into the discussion.

    • Could it be that the word “accuracy” means something different to us in quantifying ballistic performance than is means to a scientist conducting an experiment?

      The definitions of accuracy and precision in the realm of science refer only to measurements. But it would do me no good to know that I missed that deer by precisely 35.6 inches. Accuracy, to us, must mean something else. It must be a measurement of repeatable performance, or a repeatable similarity between point of aim and point of impact.

      Given your definition, no gun could possibly be accurate if it was not aimed correctly. A gun/cartridge combination cannot attain accuracy all by itself.

      But we constantly read reviews, advertisements, anecdotes, etc. from people describing a certain weapons system as “accurate.” We buy more expensive barrels, bullets, etc. in our never-ending quest for “accuracy.” And none of that makes any sense if we use the scientific definitions.

      • Well, I’m pretty sure it doesn’t do you any good to know that your rifle put a 1″ group three feet to the left of your target. Mechanical accuracy for a gun can include variables about the ergonomics and precision of the sights, sight axis / bore axis alignment, etc…

        The way I would test accuracy on a gun is to first sight it in (“calibrate” it, in scientific jargon), then see how well the rifle was able to deliver lead on target from a mechanical rest. While user error is still a significant issue to consider, it’s not as critical as shooting it freehand.

  14. Hmmmm. I chose to think of shootability vs accuracy.

    Most of my guns are more accurate than I can hold.

    With my Remington Model 7 I can shoot 1/2inch group at 100 yards from a bench. 1″groups from kneeling. And 4 inch groups from standing. Same accurate rifle but the shootability of butt-heavy, light rifle is not the best for off-hand shots (for me).

    My father-in-law used to have a Garand with a trigger-job that I could shoot 2-3inch groups off-hand at 100 yards.

    My pre-war S&W Outdoorsman (K-22) was guaranteed to cut under 2 inches at 50 yards. I can shoot 1/2 inch groups at 25 yards (from a bench) but now lack the acuity to take advantage of the 50 yard accuracy.

    The bottom line is that its nice to know your equipment is not what’s holding you back.

  15. In the physical sciences, precision and accuracy are two different concepts. Unfortunately, shooters tend to conflate them. Precision measures how consistently you get the same result. It might or might not be the result you want. Accuracy is how closely, on average, you get the result you want. The “on average” qualificaton is important. You can be any combination of precise or imprecise and accurate or inaccurate.

    Suppose you shoot a 10″ group that is well centered on the bullseye. That’s accurate but not very precise.

    Suppose you shoot a 1″ group that is 6″ to the left of the bullseye and 4″ below it. That’s precise but not very accurate.

    What you want is precision. You can adjust your sights to move your 1″ group up and right until it is nicely centered on the bullseye. Then, it’s accurate as well as precise.

  16. I like the article. But as a person who does precision metrology for a living I am never surprised to see people using the wrong terms.

    Precision = Repeatability, typically specified as +/- 2 standard deviations of a data set
    Accuracy = How close to “the right answer” you are.

    So it shooting, group size is precision, accuracy is how far away from the bullseye your group is. So many people mess up these terms in other fields of engineering that I am never surprised to see them mixed up. There is a guide to uncertainty in measurement that was put forth to get everyone (who measures things) on the same page.

    http://www.bipm.org/en/publications/guides/gum.html

    • Thank you for the reference on measurement and uncertainty – that’s just gone into my library and is very useful information.

      The guide does, however, not seem to resolve our lingo issue. Please see p. 35, where (I’m going to quote inline for people’s convenience):

      (begin)

      B.2.14
      accuracy of measurement
      closeness of the agreement between the result of a measurement and a true value of the measurand
      NOTE 1 “Accuracy” is a qualitative concept.
      NOTE 2 The term precision should not be used for “accuracy”.

      [VIM:1993, definition 3.5]

      (end quote)

      OK, we’re all agreed that precision and accuracy are two different things. I think in the context of firearms, we could agree that an accurate firearm has higher quality than a inaccurate firearm. The guide you’ve supplied doesn’t really use much of either term, however, and uses much more mathematically significant terms for statistically-based metrology. So in these mathematical terms of metrology, how would you describe a $400 rifle that throws down a 3″ group with a $2K piece of glass on top?

      • “So in these mathematical terms of metrology, how would you describe a $400 rifle that throws down a 3″ group with a $2K piece of glass on top?”

        It depends on what range you are shooting at – as well as how far off the point of aim the group is. 3″ centered on the bull at 300 yds or more is very accurate, and very precise. The same group at 50 yards 6″ off the bull is neither precise nor accurate.

        As said above by several people, how close you can come to your point of aim is accuracy. How closely together a number of shots come to each other is precision.

        Also, someone above referred to the goal of bench rest shooting as putting all the shots in the 10 or X ring. While that is the goal of a lot of target competition, how close to the center of the target (accuracy) is not the goal of bench rest shooting. The goal of that kind of competition is how small a group you can shoot (precision). The bull is used as the aiming point but how close the shots are to it is pretty irrelevant. For many years the magazine for bench rest shooting was “Precision Shooting”, unfortunately now defunct.

        The same company published “The Accurate Rifle” magazine, which dealt with more law enforcement/military/hunting applications of rifles, where hitting what you are aiming at is more important than how small a group you can get, mainly because you may only get one shot.

        All that said, I’d rather have a rifle that is BOTH accurate and precise! But that requires a whole bunch of things being done correctly and with proper care and skill, from all the components being manufactured and assembled to the shooter doing his/her part. It is a great example of a multivariate process and one of the reasons it is so satisfying to get a good result. That some can do it so well, even when under very high (even potentially lethal) stress, is awesome!

  17. DG – solid stuff for knowing precision and accuracy. The former to mechanicals of a rifle the later to the shooter. Its a shooters’ ability to bring consistency to variables that makes a marksmen.

  18. Your definitions for accuracy and precision are are mathematically incorrect. In a target shooting context accuracy is how close did I get to what I was aiming at. Precision on the other hand would apply to how tight my groups are (i.e. repeatable). I can make my gun more accurate by proper sight adjustment. However, the gun’s precision is more of a function of the gun’s design and tolerances. Otherwise a this was a nice article.

    • This. I understood what DG was explaining but there is a much simpler way to say it that the average folks would more easily understand. I’m afraid the lurkers would leave more confused about the two terms after reading this than they were before. I have lots of respect for DG but this was not one of your finest works.

      • Bad math and explanation of guns seriously hurts me to the core. I’ve spent too much time trying to convince admirals and generals of how we should do basic engagements with such systems. Some days it’s really difficult to go to work.

  20. Speaking of practical accuracy, is anyone here shooting 5 – shot 1/2 MOA groups with anything less than a scope that costs a grand and match ammo?

    • Scope yes, Weaver Classic-T 36 x 40. I load my own ammo but I do use match bullets. 200yrd 308win, Bergara LRP

      IMHO, that is my outer limit. I tried 400yrds and did not do so well. However, the range I belong to which I have the most access is only 200yrds so it also what I practice the most.

    • You could go with a good quality, fixed-power scope and shoot tight groups on a budget.

      • Damn it. I just recently got a Swarovski 4-12×50 and stuck it on my M1A, I’ll never shoot it below the 12x at 100 yards. Didn’t even think about a fixed scope. I guess I’m going to spend the rest of the night googling fixed scops.

  21. Semantics…a 3 shot, 5 shot, 10 shot 1 hole group is damn fine accuracy in my book. Not sold on the Ransom Rest either. The 1 at my club “sucks” but it is old so i would give a new 1 the benefit of the doubt. I can out shoot my club’s RR off of my old Outers Pistol Perch. Always enjoy your comments. Keep up the good work.

  23. Not sure if I can upload this image or not, but here goes nothing….
    http://imgur.com/a/Lfiwp

    Would you call this accurate, precise, both, or neither, and why or why not?

    FYI, this was fired at 11 yards, offhand, one shot about every 2-3 seconds, 2 full 16 round magazines plus one in the chamber, totalling 33 shots with CCI Blazer Brass 115gr FMJ. If you take out the fliers on the upper right hand and lower left hand corners you’re left with approximately 28 holes in roughly 3 inches. Personally I was quite happy to get this, as my eyesight is not particularly good anymore and I detest 3-dot sights with a passion. I aimed at the center of the target start to finish.

    Go!

    Tom

    • It’s the natural and usually predictable result of a collision with someone who knows what they’re doing with someone who *thinks* they know what they are doing.

      (And I’ve been often guilty of the latter…)

  27. Great article in the sense that slogging through the comments allows the opportunity to learn the concepts

  28. I agree that people confer magical properties to cnc machines that just don’t exist. They are super awesome,though.

    EDITED.

  29. It’s been a few days since I was last here on TTAG and wanted to thank folks for their responses. It’s been a busy week, with all manner of careless and stupid people needing EMT, fire department (or both) attention here in our corner of Wyoming, hence this delayed response. I suspect today’s cooler temps will only allow the wildland firefighters a brief moment to put in some holding actions before we resume hot & windy weather.

    That being said: I’ll now get in line with the new definitions for “precise” and “accurate,” if that is what people wish. A couple of points are still to be made, however:

    1. If we are to use these terms as they are now used to their full extent, it then follows that a rifle (eg) that shoots a nice, circular distribution of shots of 12″ radius around the point of aim at 100 yards (eg) is “accurate.” If you’re going to use this term to describe just such a rifle, I might also suggest that you pursue a career in selling snow to the Inuit, sand to the Arabs and the aforementioned ‘accuracy’ rifles to mathematicians, because you will be a salesman (or woman) without peer.

    2. While describing a rifle that throws down a tight, bug-hole group as precise, the common tendency of describing such a rifle as ‘inaccurate’ when the tight group deviates from the point of aim is hogwash. The rifle shoots where it is going to shoot. When you have a scope that allows you to determine your point of aim to a very small area on your target, and your precise grouping doesn’t coincide with your target point, do you bend the rifle barrel to adjust the group to coincide with the point of aim for the scope?

    Of course not. Not even in some of the more bizarre things I’ve seen brought to me has anyone ever come in saying “I want my barrel bent to bring it into zero with my scope.” Of course we adjust the scope. So which was inaccurate? The gun? No. The scope (or sights) was inaccurate (ie, not putting the point of impact on the point of aim).

    I have bent shotgun barrels, but that’s a whole ‘nother story, and they were bent before they came to me. I was just “bending them back.” Why someone decided to stuff a perfectly good shotgun barrel into a 2″ receiver hitch on a pickup and bend the barrel to overcome a stock that didn’t fit them… that I’m still unable to explain.

    3. As I said above, precision can come from a scope. If you have a good scope on a ‘precise’ rifle, are you not able to throw down a tighter group than if you had just (eg) buckhorn sights? More than once, people have found out that (especially as we age) that their groups tighten up when they can really discern the target properly.

  30. Admirers have always strong cheered thus to their organizations. That’s what makes qualified sporting activities: the fans. Enthusiasts are an busy portion of activities. Constantly it hears joggers express, “Thanks to your fanatics, ” or even “It’s interesting features of most of these great supporters we are below. ” A whole lot of FOOTBALL team incorporates a twelfth man gratitude; the exact Detroit Seahawks perhaps designed their whole stadium to be able to encapsulate and also magnify audience noise for the impression fans possess.

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