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  • Barrel length vs. powder speed

    I've always had this thought in my head that you can counteract a barrel cut with a little faster powder, is there any truth to that?

  • #2
    It works a little bit in 45 Colt going from 5.5 to 4.625 to 3.75, but group size suffered for me with mine.

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    • #3
      The shorter the barrel the bigger the change or effect on the impacts of the round. We have found on our SBR you will lose VELS with the standard 62 grain 5.56. How noticeable is it at 100m not much but more the farther you go out. There is talk of getting a fast powder for these shorter barrels rifles to compensate for the lose of energy.
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      • #4
        Originally posted by limon32 View Post
        I've always had this thought in my head that you can counteract a barrel cut with a little faster powder, is there any truth to that?
        No barrel length has absolutely nothing to do with powder burn rates. Burn rate is dictated by the cartridges, not the length of the barrel. The same burn rate powders that give the highest velocity in longer barrels, will also give the highest velocity in shorter barrels.

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        • #5
          limon; much of the time barrel length is really determined by the cartridge used if maximum velocity and energy are required. shooting my sniper rifle with a 26" barrel in .308 vs a 20" barrel yielded little change. that's because the .308 class cartridge burn efficiently and completely in 18"-20" with standard powders.

          shooting a magnum cartridge requires a slower powder, more burn time, and a longer barrel to make that possible.

          with short range heavy caliber rifles used for dangerous game, the range is short enough that small differences really don't matter. choose the caliber/ barrel length to your needs and don't look back.
          happy trails.
          jh

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          • #6
            Years ago (like 30), Weatherby brought out a "carbine" version of their Vanguard with an 18" barrel in an array of calibers, including 7mm Rem Mag. Buddy of mine picked one up and he was as proud as a puppy with a new chew toy. He insisted on chronoing it, but I put him off for about a year, during which he hunted with it a lot and did well. None of us wanted to be near when he shot it, but he sure liked carrying that handy little thing.

            The fateful day came when he brought it over for me to launch rounds over the screens. Darned near broke his heart. Factory loads were turning out less vel than my 7x57 with modest handloads through it's 22" tube. Lots of whoop and roar when you touched off his gem, but unbelievable that so much flame and noise put such little numbers on the meter. I don't recall the specifics right now, but that's enough of an intro.

            He begged me to do some loading to see if I could change the #'s with a different powder. He kept my notes, so I can only be general. The final powder I settled on was 4320. Outstanding accuracy with about 10% of the muzzle flash and vels only a little less than the factory loads. My play with surplus 4831, my favorite powder for the 7mag, was interesting. The favorite load for my 24" barrel turned out 400fps less vel from his 18" barrel- 3100fps vs 2700fps. I don't worry much about a loss of 100fps or even 200fps, but a loss of 400fps drops you into a whole different performance realm in both trajectory and terminal performance. Kind of like comparing a 300 mag with a 300 Savage.

            Nutshell- I was more or less able to match the miserable performance of factory loads and slow powder reloads with a switch to a faster powder. But I wasn't able to beat it. He had a very handy, very loud and flashy 7x57 with factory loads and a polite 7x57 with faster powder in handloads. Even though the rifle was a joy to carry and he killed lots of game with it, he was heartbroken and peddled it.
            "Lay in the weeds and wait, and when you get your chance to say something, say something good."
            Merle Haggard

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            • #7
              Optimally, powder should have burned and fully expanded just prior to the bullet leaving the barrel. Too early a burn (too fast a burn or not enough powder) is a loss of velocity. Too much powder and some/ most is burned outside of muzzle is no advantage, just a waste of powder giving you a pyrotechnic show with every shot.

              So the trick for hand loaders is to find the right combo of amount and burn rate of powder to match your barrel length for optimum grouping, not velocity.


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              • #8
                Although it doesn't seem to make sense, what jwp500 said is the truth.

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                • #9
                  Thanks fellas, you've been super helpful as always!


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                  • #10
                    Originally posted by jwp500 View Post
                    Burn rate is dictated by the cartridges, not the length of the barrel.
                    Ummmm.... No. Just look at the manuals. Burn rate has to do with the chemistry of the powder, whether in a cartridge, barrel or the palm of your hand. Some powders do all their burning inside the cartridge and some do a whole lot of it outside the barrel. VELOCITY is determined by burn rate and barrel length.
                    "Lay in the weeds and wait, and when you get your chance to say something, say something good."
                    Merle Haggard

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                    • #11
                      Burn rate is modified by size of container, weight of bullet, and bore size. Still, the powders that produce the highest velocities in long barrels usually produce the highest velocities in short barrels as well.

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                      • #12
                        Originally posted by rbuck351 View Post
                        Burn rate is modified by size of container, weight of bullet, and bore size. Still, the powders that produce the highest velocities in long barrels usually produce the highest velocities in short barrels as well.
                        After reading the responses here I did a bit more reading on some other forums and this appears to be the prevalent experience.


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                        • #13
                          Powders

                          Originally posted by limon32 View Post
                          After reading the responses here I did a bit more reading on some other forums and this appears to be the prevalent experience.


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                          That is generally the safe bet if your dealing with published data and chasing velocity...But honestly my instincts always send me searching for a powder with at least a 95 percent burn rate by the time it leaves the barrel . And that fills about 90-100 percent of the loaded case capacity.. This leads to less recoil, less muzzle flash a more consistent and a cleaner burn. I am not all saying slower powders are bad..indeed upon test some slower powders yield great results. However I usually start searching for a load that meets the listed criteria of 95&95.. I test for better results from there. I heard somewhere that any time you exceed 95 percent case fill that barrel wear increases exponentially. I can't prove that true and it seems a large percentage of reloaders like a slightly compressed load... If 8 out 10 reloaders agree on a issue... There's usually a method in the madness.. I've had great results either way, thus I don't argue and usually I do what prints best on paper..

                          If you would like ...if you send me the length of your barrel from crown to bolt face.. The type of bullet (weight & manufacture) you intend to use and the h20 capacity of your brass. I can run those through quick-load and compare powders for you.

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                          • #14
                            I do not take this as gospel however This guy does a good write up...http://www.gunnersden.com/index.htm....ng-powder.html


                            I also like this one..http://www.shootingsoftware.com/loadens.htm


                            I also searched for a description of the rocket effect that slower burning powders have when they exit the muzzle this increase recoils and sometimes effects accuracy... but cannot find it right now... On another note I have also found I'm my own experience that sometimes you can get better velocities with certain quicker powders then slow ones because you can simply fit more quicker burning powder in a given case......(that comes with higher pressures of course) and if you enter that arena your usually not following load manuals and your on your own...but h335 or aa2230 vs Tac or BLC2....In a 5.56 Carbine Length is a prime example of this.. in a longer 20inch barrel the BLC-2 gives better velocities then h335 because it has time to burn However your case is most likely full..Now with the carbine length system 16" or less this extra powder burn efficiency of BLC2 is not realized therefore you can duplicate and even out preform it with h335 simply cause you can stick more in a given case... once again remember the higher pressures come with it and I would approach that method cautiously.

                            for what your doing I would recommend quick load software.... It certainly answers a bunch of questions where an otherwise reloading Manual might be mis leading

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                            • #15
                              Originally posted by AlaskanTides View Post
                              I do not take this as gospel however This guy does a good write up...http://www.gunnersden.com/index.htm....ng-powder.html


                              I also like this one..http://www.shootingsoftware.com/loadens.htm


                              I also searched for a description of the rocket effect that slower burning powders have when they exit the muzzle this increase recoils and sometimes effects accuracy... but cannot find it right now... On another note I have also found I'm my own experience that sometimes you can get better velocities with certain quicker powders then slow ones because you can simply fit more quicker burning powder in a given case......(that comes with higher pressures of course) and if you enter that arena your usually not following load manuals and your on your own...but h335 or aa2230 vs Tac or BLC2....In a 5.56 Carbine Length is a prime example of this.. in a longer 20inch barrel the BLC-2 gives better velocities then h335 because it has time to burn However your case is most likely full..Now with the carbine length system 16" or less this extra powder burn efficiency of BLC2 is not realized therefore you can duplicate and even out preform it with h335 simply cause you can stick more in a given case... once again remember the higher pressures come with it and I would approach that method cautiously.

                              for what your doing I would recommend quick load software.... It certainly answers a bunch of questions where an otherwise reloading Manual might be mis leading
                              I forgot to not that my caparison of h335 to Tac was in reference to a 55 grain bullet....once you get to 62 grains and heavier even out of a 16 inch tube the slower tac is running at an efficient Ba and the quicker h335 docent stand a chance however in the 55 grain category the h335 can compete in certain situations.......a prime example of why test and try differant things...

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