Projectile speed when fired from different length barrels?
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    Default Projectile speed when fired from different length barrels?

    What would be the increase in speed when the same 38 round is fired from a 6" compared to a 4" or 2" long barrel hand gun?

    I watched a R. Lee Ermey Lock N Load show that was on the history of artillery. A longer cannon barrel does increase the speed of the projectile.
    The proof of that was the comparable damage done to the targets down range.

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    The type of propellant will make a big difference in results.
    Some are made to burn quickly, while others more slowly.

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    buy a Quickloads program.
    IDK about 38's in those short barrels but in 22lr match barrels, anything over about 26" slows the bullet down supposedly.
    Then you have stuff like centerfire Palma guns with 30" barrels to get that extra velocity

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    Default All cats are dogs.

    The question is subjective to more factors than just barrel length... and while I have a certain amount of respect to Gunny, comparing damage results is not a metric by which muzzle velocity can be accurately represented. A simple concept proof is this: Fire a .38 Special at a paper target at 10 feet. Fire a .357 Magnum at same paper target, from same distance, with same firearm. They'll both present the same hole. If this is the agreed metric, we could deduce that the .38SPL and .357Mag were travelling at the same speed, thus, no difference exists in the two cartridges... however, anyone who was the recipient of those cartridges at that distance, would clearly say otherwise.

    All cats have four legs.
    All dogs have four legs...

    Therefore... All Cats... are dogs.



    When there's still fuel to burn, the lack of a barrel will result in just fire and noise.

    When there's no fuel left to burn, additional barrel will result in loss of velocity.

    To determine the proper of effective barrel length, one must establish all of the variables, including the burn rate and pressures of the powders being desired, as well as the projectile mass.

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    Quote Originally Posted by DaveKamp View Post
    To determine the proper of effective barrel length, one must establish all of the variables, including the burn rate and pressures of the powders being desired, as well as the projectile mass.
    Then there are the variations in the barrel. I have seen some velocity test with a pile of different hand guns and once in a while the one with the shorter barrel had a puzzling higher velocity. One could fashion a test by starting with a long barrel gun and progressively testing it by shortening the barrel. but that would only tell you about that particular barrel and ammo configuration.

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    Quote Originally Posted by DaveKamp View Post
    The question is subjective to more factors than just barrel length... and while I have a certain amount of respect to Gunny, comparing damage results is not a metric by which muzzle velocity can be accurately represented. A simple concept proof is this: Fire a .38 Special at a paper target at 10 feet. Fire a .357 Magnum at same paper target, from same distance, with same firearm. They'll both present the same hole. If this is the agreed metric, we could deduce that the .38SPL and .357Mag were travelling at the same speed, thus, no difference exists in the two cartridges... however, anyone who was the recipient of those cartridges at that distance, would clearly say otherwise.

    All cats have four legs.
    All dogs have four legs...

    Therefore... All Cats... are dogs.



    When there's still fuel to burn, the lack of a barrel will result in just fire and noise.

    When there's no fuel left to burn, additional barrel will result in loss of velocity.

    To determine the proper of effective barrel length, one must establish all of the variables, including the burn rate and pressures of the powders being desired, as well as the projectile mass.
    Dave, you are taking readings that are both off scale and then saying they are alike. If you substituted 1/8" mild steel plate or a dozen 1" white pine boards, you would be making meaningful readings.

    There are lots of variations but the velocity variation with barrel length is still there. I seem to recall that you could figure 22 fps for each inch of barrel length with 30-06 class rifles with around 20" barrels.

    There are documented cases of 2" barrel .38 bullets bouncing off skulls. One happened in St. Louis,where a detective shot a perp and the bullet slid round his skull under his scalp. Sammy The Bull Garbano related a similar case. You don't hear these stories about 4" barrel .38s.

    Incidentally, I have been told that the velocities listed in manufacturer's data sheets are often taken from a long barreled pressure gun so we would have to all be carrying Buntline Specials to get the listed performance. That is old information and now that a lot of people have chronographs, they couldn't get away with it.

    There was a study where Barbary goats were led into a box with some food strategically placed to line the goat up with a test gun and they timed how long it took the goat to die after being shot. They terminated the 2" barrel .38 because the goats were taking too long so they stopped for humanitarian considerations.

    How touching.

    Bill

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    Theoretically a longer barrel could produce a higher velocity. But, as mentioned earlier, too long a barrel will slow down the bullet.
    As for the short barrels being ineffective, I would have to look all the variables before reaching that conclusion.
    In actual tests, the 6" Colt was sometimes slower than the snub nosed Smith.
    There are so many factors to be considered, that the most reliable tests are derived from one gun and one lot of ammo. Start with a long barrel and shorten it as you go.

    Chart...
    http://ballisticsbytheinch.com/docs/GaptestDataRW.pdf


    Short list of powders...

    burn-20rate-20chart.jpg

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    Quote Originally Posted by 9100 View Post
    Dave, you are taking readings that are both off scale and then saying they are alike. If you substituted 1/8" mild steel plate or a dozen 1" white pine boards, you would be making meaningful readings
    Perhaps that was misunderstood- I was being somewhat facicious, in that both of the incidences resulted in the 'same size hole', which as anyone with projectile weapon experience knows, the size of the entry point is practially an irrelevant metric in determining any other aspect of the result. There's so many misnomers and assumptions about the effectiveness of a projectile, that drawing a simpleton's observation (hole in paper) displays to those in-the-know... how an audience of limited understanding is so easily predisposed. I could just as easily say that a .45 long colt makes a bigger hole in the paper than a 7.62-54R, therefore, it is more effective. The metric may appear concrete, but the reality is a farce of fallacy.

    The whole concept of a projectile inside a barrel, is internal combustion generating pressure, pushing on a piston. When the fuel is gone, pressure falls, and eventually, when friction overcomes pressure rise, acceleration stops, therefore, the projectile will slow down. If there's not enough fuel to do the job, a shorter barrel will reduce the slow-down. If there's too MUCH fuel, the projectile will leave the barrel behind, whilst fuel still burns. As a side-effect, excess pressure relieved as the projectile clears the muzzle, will 'blow' the tail of the projectile, and destabilize it in flight. I'm pretty certain that everyone is saying the same thing... that while there's a relationship between barrel length and velocity, that there's many more factors included in the relationship, that are equally, if not substantially more imnportant... than just the length of the barrel.

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    Quote Originally Posted by FredC View Post
    Then there are the variations in the barrel. I have seen some velocity test with a pile of different hand guns and once in a while the one with the shorter barrel had a puzzling higher velocity. One could fashion a test by starting with a long barrel gun and progressively testing it by shortening the barrel. but that would only tell you about that particular barrel and ammo configuration.
    Some tests were done on rifle barrels with the exact same bullet/load and they found a variation in muzzle velocity between makes of barrels - by as much as 175 fps on a 24" barrel at the muzzle. Some barrels in benchrest are known to be "faster" than others - but not necessarily more accurate/precise.

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    Quote Originally Posted by wyop View Post
    Some tests were done on rifle barrels with the exact same bullet/load and they found a variation in muzzle velocity between makes of barrels - by as much as 175 fps on a 24" barrel at the muzzle. Some barrels in benchrest are known to be "faster" than others - but not necessarily more accurate/precise.

    Links to these tests?

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    Quote Originally Posted by tdmidget View Post
    Links to these tests?
    I'll have to dig back through my notes to find it. In the end, the results weren't that surprising, as not all barrels are finished the same (some are lapped, some are not), and they might differ in bore diameter by a tenth of a thou or two. The nut of the issue is that "this" barrel isn't necessarily the same as "that" barrel, and there's a reason why some BR shooters talk of "hummer" barrels where everything seems to come together and perform outstandingly well, which when replaced with the same make/length of barrel, cannot reproduce the same load results.

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    Quote Originally Posted by rons View Post
    What would be the increase in speed when the same 38 round is fired from a 6" compared to a 4" or 2" long barrel hand gun?

    I watched a R. Lee Ermey Lock N Load show that was on the history of artillery. A longer cannon barrel does increase the speed of the projectile.
    The proof of that was the comparable damage done to the targets down range.
    the length only will increase the speed if the powder/gases are still expanding along the length of the barrel....

    Lets say for example your "38" ammo produces a volume of gas that stops expanding in the space behind the bullet after 4" a 6" barrel will not be any faster, if the barrel is shorter the gas has not finished expanding to its peak....

    Im pc dumb and it takes me forever and a day to figure out how to get images from quickloads onto the screen or I would just find a basic load and change the barrel lengths..of course this can all change with the quality of barrel types of rifling chambers and such.
    I can tell you my target loads 38spl 158 SWC fired in a 2" SW chief special vs the 6" 19-2 are only about a 50 fps change ?

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    All good info in here. The type of powder as already mentioned is also key in velocity. A slow burning powder will yield a higher velocity in a longer barrel. A faster burning powders will yield a higher velocity in a shorter barrel. Combinations of that can be all over. Button rifled barrels are slower than polygonal barrels, etc. The projectile bearing surface also has an effect on the velocity, as does the seal of the projectile. There are hundreds of variables. Barrel length combined with the proper powder should increase velocity if done properly. Longer barrel lengths, however, have little positive impact on accuracy, which is a common misconception by many. There's lots to learn about accuracy, more than a lifetime.

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    Quote Originally Posted by Pyrex View Post
    All good info in here. The type of powder as already mentioned is also key in velocity. A slow burning powder will yield a higher velocity in a longer barrel. A faster burning powders will yield a higher velocity in a shorter barrel. Combinations of that can be all over. Button rifled barrels are slower than polygonal barrels, etc. The projectile bearing surface also has an effect on the velocity, as does the seal of the projectile. There are hundreds of variables. Barrel length combined with the proper powder should increase velocity if done properly. Longer barrel lengths, however, have little positive impact on accuracy, which is a common misconception by many. There's lots to learn about accuracy, more than a lifetime.
    If you look at the old school 22 target rifles they have 24-30" barrels. They are that long IMHO to increase sight radius. Today the barrels are shorter but some will attach " bloop" tubes to increase sight radius.
    VElocity/bullet rpm play a role as does finding that barrel "accuracy node" thankfully lots of this has been hashed over and figured out over the past 100 years. Only real thing left for us to do today is find the load that works in our guns the best.

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    What would be the increase in speed when the same 38 round is fired from a 6" compared to a 4" or 2" long barrel hand gun?

    Revolvers and revolver cartridges are a separate beast from others because of the cylinder gap which bleeds pressure as long as the bullet is still in the barrel. And with a medium power cartridge like .38 Special, the small powder charge could easily run out of pressure before the bullet reaches the end of a 6" barrel.

    The only way to get credible data would be to take a 6" barreled revolver and chronograph at least 10 each of various loads, cut and crown the barrel to 4" and retest, cut and crown to 2" and test a third time. Differences between different guns would introduce too many variables for a valid comparison.

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    Re extra gasses disturbing accuracy, I did some tests with my Browning Medalist .22 pistol. I clamped the barrel in a milling vice, with appropriate padding to prevent damage to the finish, and fired 10 shot groups across my basement. That produced one ragged hole, so I moved the mill table over after each shot and measured the deviation from a straight line. With match grade pistol ammunition the line was almost straight. Match rifle ammunition had a major decrease in accuracy and the high velocity loads like Super-X were all over. I attributed it to gasses disturbing the bullet. I have long wanted to put a ring of Magnaports around a barrel to relieve the pressure before the bullet leaves the barrel.

    Bill

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    Some of the Olympic rapid fire pistols have several ports drilled in the barrel in front of the chamber to relieve pressure (and, presumably, decrease recoil.) I think one hole an inch from the muzzle would be adequate for testing and it could be threaded for a plug if you wanted to disable it. The through hole at .040" should be enough at the bottom of a 6-48 threaded hole. Might have to lap the bore so no burr is left.

    On the other hand, don't use rifle match or high speed in a target pistol. :-)

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    Quote Originally Posted by 9100 View Post
    Re extra gasses disturbing accuracy, I did some tests with my Browning Medalist .22 pistol. I clamped the barrel in a milling vice, with appropriate padding to prevent damage to the finish, and fired 10 shot groups across my basement. That produced one ragged hole, so I moved the mill table over after each shot and measured the deviation from a straight line. With match grade pistol ammunition the line was almost straight. Match rifle ammunition had a major decrease in accuracy and the high velocity loads like Super-X were all over. I attributed it to gasses disturbing the bullet. I have long wanted to put a ring of Magnaports around a barrel to relieve the pressure before the bullet leaves the barrel.

    Bill
    In .22 target work, your best accuracy is almost invariably had by using an ammo that is slightly sub-sonic in the firearm you intend to use (whether it be pistol or rifle).

    I've done similar testing, and have talked with several .22 match shooters, and their data, my data and other data is consistent with yours: the "high velocity" ammo is all over the place.

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    It was a long time ago and the ammunition has changed, but I also found a measureable difference between Eley match and practice ammo but the difference was so small that practicing with it was valid. With high velocity stuff, you couldn't tell whether a flier was you or the cartridge. With Eley practice, you could be sure it was you.

    Bill


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