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How much accuracy is gained by an inch of barrel?

Discussion in 'Handguns: Autoloaders' started by Potatohead, May 5, 2013.

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  1. 918v

    918v Member

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    The point is to show an unbiased baseline for accuracy. I could not find any 5" PPQ targets. As soon as I do I'll post them.
     
  2. 1SOW

    1SOW Member

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    1" of additional bbl length 'can' increase a "gun's" accuracy. It depends on the original length of the bbl.
    USE .22lr or 45 ACP as an example (often used for bullseye target comp.):
    A 3"-4" bbl pistol in a ransom rest will not be as accurate as a 4"- 5"" bbl in a ransom rest. More accuracy improvement can be seen normally at about 5" +.. Bullet Ballistics improves quite a bit with added bbl length up to a point.

    As said throughout the thread: Sight radius , pistol weight and other factors also make it easier to shoot accurately.
     
  3. Walt Sherrill

    Walt Sherrill Member

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    You may be correct, but most of what has been shared in this discussion suggests otherwise. I'll repeat some of the points already made... Unhappily, I've never seen Ransom Rest test results assess that single variable. I've seen them for specific guns, and seen them used to compare one custom gunmaker's version of a given model (ala 1911) to another gunmaker's creation.

    A Ransom Rest takes the human variables out of the mix, so that finger on the trigger and sight/target alignment aren't factors; the test simply assesses the gun's ability to return to the exact same starting position for each shot -- demonstrated by small groups when the gun is fired. They're useful for steel-framed guns, but can't be used with most polymer-framed guns.

    The information shared here suggests that if everything but the barrel length is the same, the results of a Ransom Rest test might not differ greatly between longer or shorter barreled guns, until barrel lengths are quite different. If we're talking only about an inch or two, the "improvement" in performance due to higher bullet speed and spin rate, etc., may not be significant. It may depend on the load.

    The American Rifleman article previously mentioned did an equivalent test - took a handgun caliber rifle with a long barrel and started lopping it off, an inch or so at a time, recrowning the barrel, and retesting. They didn't notice much change in precision/group sizes until the barrel got so short as to impair the stability of the round. There were differences of course, but they were not profound. (I'm looking for the original article; all I've read are summaries that may be inaccurate.)

    At closer ranges, like those most often encountered in self-defense situations, barrel lenght might not matter. I wonder how much of self-defense shooting is truly "aimed fire" -- a lot of it seems to be variations of "point-shooting" or just blasting away. I suspect that if the shooter uses the sights, the longer sight radius of the longer barrel will help the shooter as much as any improved round performance from that longer barrel.
     
  4. powder

    powder member

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    Depends. :neener:
     
  5. Potatohead
    • Contributing Member

    Potatohead Member

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    thx for your comments fellas
     
  6. Walt Sherrill

    Walt Sherrill Member

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    I found the following on the S&W Forum, among discussions between Bullseye shooters. They were talking about revolvers, but I suspect some of the concerns still apply to semi-autos that have locked-breech designs (or fixed barrels).

    One of those responding earlier mentioned the effect of harmonics and vibrations -- and this shooter also feels it's important with short pistol barrels, too. The barrel and slide, in a locked breech system, has already begun to move before the bullet leaves the barrel, but the barrel/slide hasn't moved far. It is probably influenced by harmonic vibration in a different way than is a fixed barrel, but still infuenced.

    I added the underlining and bolded characters, below.

    From a purely engineering standpoint, with a one piece barrel the shorter barrel will actually be more accurate than a longer barrel. When a barrel is attached to the frame at just one end it becomes in effect a Cantelever Beam. Since a bullet transitting the barrel will cause that beam to bounce like a diving board, a shorter barrel will be "stiffer" in it's response and the end will deflect less during the transit event. I suspect that if a 2 1/2 inch 686 and a 6 inch 686 were both equipped with a good handgun scope and fired from a rest by a real good shooter, the short barrel would just trounce the longer barreled gun in group size. However, in order to prove this out completely, each gun would have to use a load that was optimized for the barrel length. Because Harmonics can have a distinct effect on any vibrating system and barrels do vibrate in response to a bullet transitting them. Ideally you want a load and bullet mass where the end of the barrel is passing through it's Neutral position when the bullet exits the muzzle. Ask anyone who's worked up loads for long range rifle shooting, just a 100 fps difference in velocity can make a distinct difference in group size downrange.​

    There are other comments which indicate that some top-flight shooters prefer and shoot shorter-barreled guns better than longer-barreled guns -- even when they're competing against shooters using those longer barrels.

    .
     
    Last edited: May 14, 2013
  7. Vern Humphrey

    Vern Humphrey Member

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    There is a problem with that -- if we assume the barrel that is "bouncing like a diving board" is following a sine wave pattern, then the effect can be either beneficial or negative. If bullets are exiting at the top or bottom of the wave, the gun will be very accurate -- because there is very little motion at that point.

    On the other hand, if bullets exit between nodes then accuracy will be poor.

    You may remember Browning used to offer a device on the barrel to "tune" the barrel to the harmonics of your load. That's how it worked -- as you turned the device one way, if groups got smaller, it meant the harmonics were being tuned so bullets exited at the node.
     
  8. Target008

    Target008 Member

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    in my experience not much and that can include some really large jumps like 3"-6" now while i do not personally believe that much accuracy is gained velocity on the other hand is a different story.
     
  9. 1SOW

    1SOW Member

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    I don't disagree. The word "greatly" is included above. The point was the would adding an inch to bbl length improve accuracy. My point was that depends on the starting length. AT ONE EXTREME: A one inch bbl (I had one--a 5-shot stainless 22 lr revolver ) will not get the accuracy as a two or three or 5" bbl in the same pistol with any load.

    Velocity does matter, and discounting that as a factor included with a longer bbl is ignoring the facts. The OP didn't say or ask about velocity.
    "Handgun Ballistics per inch of barrel" is an amazing test of virtually all calibers of handguns from .22 to 460 Rowland. using "FIXED" bbls from 2" to 18". Amazingly long distances in the bbls showed continued acceleration and resulting spin of the bullets.
    http://www.ballisticsbytheinch.com/

    "Pocket Pistols" atre not going to perform as well a longer bbl pistol. There isn't enough bbl twist to fully stabilize the bullet. I would suspect one specific bullet weight would show the optimum accuracy in that gun. Adding an inch here can make a difference in accuracy dmonstrated with longer ranges..

    See how many Bullseye pistol shooters use a three inch or less bbl at 25yds or more. They would if they were more accurate. Yes, I know, but there are shooters that can hold the 3" sight radius on target with a balanced/weighted pistol..:D

    Would make an interesting test in a specific pistol with maybe three typical loads of light, medium amnd heavy charges..:cool:
     
  10. Walt Sherrill

    Walt Sherrill Member

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    That is an interesting site and I've bookmarked it. Thanks.

    Unless I missed, it however, it doesn't address a relationship between muzzle energy and accuracy/precision. It just shows what energy is gained for specific changes in barrel lengths. You seem to feel there is a relationship.

    I did a quick spreadsheet on the data for 9mm Luger -- for 4, 5, and 6" barrels. Generally, the increase in muzzle energy moving from 4"-5" is roughly 1%-2%, and from 5" to 6" roughly 4%-6%. The biggest jump (from 5" - 6") -- that seems to be the sweet spot.

    If you run the spread sheet on out, you'll see that the energy increase with each added inch of barrel is smaller, and at 18" length, for most loads, muzzle energy actually decreases

    In the case of the 4"-5", a 1%-2% improvement in muzzle velocity isn't likely to be noticed; the from 5" to 6" is more meaningful, but I'm not sure it translates to a comparable increase in accuracy.

    In the case of .45 A.C.P, the results were a little different, with the biggest increase coming in the 4"-5" jump (from 2%-7%, depending on the load), but less with 5"-6", where it varied from 0% to 3%, Muzzle energy generally increased with increased barrels, lengths -- but as with 9mm, at a decreasing rate, and actually declined at 18".

    How do we correlate muzzle energy to accuracy/precision? Got any other sites? All of this would seem to suggest that for some rifles firing pistol cartridges, barrel length should be something to which the shooter/buyer pays close attention. And, as others have noted, bullet weight and design may be a critical factor, too.

    .
     
    Last edited: May 18, 2013
  11. Walt Sherrill

    Walt Sherrill Member

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    Since replying, above, I've done a lot of digging on the web and found basically nothing except anecdotal evidence that addresses the relationship of barrel length or muzzle energy to accuracy. I did find this interesting comment on the S&W Forum, where one member responded to another's claim of calculations that showed that a 3-4 inch barrel would give larger groups than a 5 inch barrel. That person said there was a calculation, but didn't share it, and didn't give evidence that could be verified. The responder said:

    It is just barely possible that in the 3 - 4 inch barrel range, the mathematical calculations are relevant. However, in the summer of 1931, then-Major Julian Hatcher fired a "possible" at the British Nationals at Bisley with an H&R pistol with 8" barrel rather than the customary 10" barrel, with Ensign Harry Renshaw taking second place with a 98, using the same H&R pistol. The following year, interest in short-barreled H&R pistols increased considerably. Walter Roper subsequently did a limited study of the effect of sight radius on accuracy (three shooters, extensive shooting with more than one sight radius), and concluded, IIRC, that the shorter sight radius was better for one (top) shooter, longer for another, and unclear for the third. Roper reports all of this in his book Experiments of a Handgunner. There was also published an article by him in the September 1946 American Rifleman, in which he noted that after over a hundred shooters purchased short-barreled H&R pistols, a majority of the 65 who reported back to him reported better scores with the short pistol.

    It seems quite clear to me that the arithmetic involved is often less important than other variables in the individual shooter, and the actual practical result can usually be determined only by extensive experimentation.​

    That was a long time ago. Now, many Bullseye shooters and handgun hunters seem to believe that OPTICAL SIGHTS (scopes, red dots, etc.) make sight radius an unimportant variable.

    They also seem to feel that if not using optical aids, some barrel lengths might be better with a given pair of eyes, than another. Then note, too, that many (perhaps most) factory handgun loads come optimized for the fairly standard 4" barrel. -- and that in all cases, that optimal performance will come only when the load used is FITTED to the a bullet weight and shape, barrel length, and twist rate.

    In the case of rifles, it appears that longer barrels are absolutely greatly superior when shooting at ranges beyond 250 yards (or far longer) -- as much as because they are more likely to reach out that far as for the ability to group -- but that much shorter rifle barrels can be just as (or more) precise at closer distances (100-250 yards).

    Nobody seems to any hard data. (I can't find it... it may be out there.)
     
  12. Vern Humphrey

    Vern Humphrey Member

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    He might have been seeing the Hawthorne Effect -- they bought the shorter barrels expecting better scores and they got better scores.
     
  13. Walt Sherrill

    Walt Sherrill Member

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    RE: Hawthorne Effect.

    Could be, but it works the other way, too, doesn't it?
     
  14. Vern Humphrey

    Vern Humphrey Member

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    Yeah -- but no one buys a gun expecting to shoot worse, so the sample consists almost entirely of people who expected to shoot better.
     
  15. Walt Sherrill

    Walt Sherrill Member

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    Expectations can drive a lot of results. Your statement above could also be applied to those who KEPT their existing weapons or decided to buy 10" barrels, too. They wouldn'tve bought or kept their 10" guns expecting to do worse...

    The Hawthorne Effect really addressed GROUP DYNAMICS and GROUP PRODUCTIVITY and the PERFORMANCE OF TEAMS working on group objectives. In the cases I've cited earlier, there were no teams, just individuals reporting their changed scores -- and it may be that they were unaware of how others using the same barrels were doing...

    .
     
    Last edited: May 19, 2013
  16. Vern Humphrey

    Vern Humphrey Member

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    Perfectly true -- but the informal study cited above included only people who bought shorter-barreled guns.
    Actually not -- most of the Hawthorne employees had repetitive tasks and worked on piecework.
     
  17. Walt Sherrill

    Walt Sherrill Member

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    Piecework was one of the variables after the initial study was expanded. It went on with a small group of women for a much longer period, and that's where they started to see really interesting results.

    Nearly every article you can find about the Hawthorne effect discusses it as an important milestone in industrial and organizational psychology. It's generally described as being about group dynamics and how management interventions -- some seemingly meaningless -- can affect group behavior and performance. The Hawthorne workers initially had NO EXPECTATIONS of performance improvements, but they quickly learned they were being watched. THAT can affect performance.

    As the studies progressed, the workers were given a lot of feedback, and even had opportunities to suggest changes. At one point, workers were paid based on group performance rather than individual performance -- piecework standards went out the window for a while; they were even allowed to change the length and frequency of breaks and the duration of the work day. Generally, performance improved, regardless. Sometimes it improved even when things went back to an earlier state or condition. It was all about being observed and getting (and, perhaps, giving) feedback.

    Unlike the workers in the Hawthorne study, the shooters we're talking about were queried AFTER the fact. The fact that some shooters did better because they expected to do better is a real possibility -- a self-fulfilling prophecy, so to speak -- but it may also be that the shooters who went to the shorter barrels got better because they were the ones who were trying harder, or because they were learning and improving with practice and the experience they gained from an additional year of matches. They may have improved with 10" barrels, too.

    After posting that "statistic" I mentioned, I got to thinking about what it really told us: that 100 were queried and only 65 responded. Of that 65, it could be that as few as 33 saw improvement. That, in turn, could mean that as many a 67 of the 100 (i.e., 32 + 35) may NOT have seen any improvement.

    Statistics can sometimes be interpretations (and intensely subjective). Or, as Mark Twain called it: "Lies, Damned Lies, and Statistics."
     
  18. Vern Humphrey

    Vern Humphrey Member

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    All perfectly true -- which was my point. The "study" which found there might be an improvement from a shorter barrel showed no such thing, and improvements may have come because the people who bought shorter-barreled guns expected to improve.
     
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