Barrel length vs. powder rule of thumb?

Discussion in 'The Ammo & Reloading Forum' started by jrw1976, Mar 14, 2010.

  1. jrw1976

    jrw1976 New Member

    Mar 14, 2010
    I have been reading and research none stop for the last couple of months since I have started reloading and now I have a question that I haven't found an answer to. What I would like to know is, is there a quote "rule of thumb" that has to do with the amount of powder to use for a bullet shot out of say 22 inch barrel versus a 24 inch barrel? Should the powder be more or less in the 22 inch versus 24 inch? I have noticed that the test barrel length in the manuals I have are normal 24 inch barrels. Or am I just over thinking this and barrel length doesn't have as much pertenance as I think it does? Thanks JRW
  2. Lee C.

    Lee C. New Member

    Feb 3, 2010
    Antigo Wi.
    Youl get a little more fps out of a longer barrel. But pick out the bullet youl be shooting, Then fine the powder and the right powder weight for that bullet. I dont know of any short cuts for doing this. But i'm sure if there is some one should jump in here soon.

  3. ofitg

    ofitg Active Member

    Feb 25, 2010
    Thirty years ago I bought a cardboard slide-rule gizmo called the "Powley Handload Computer".... I imagine that somebody has implemented this into a software program by now....
    Anyway, the way the Powley gizmo works, the case capacity determines what the powder charge weight should be. The ratio of charge to bullet weight, and the bullet's sectional density, determine what the powder TYPE should be. So far, barrel length doesn't have anything to do with it.

    The expansion ratio is determined by the bore diameter, the barrel length, and the case capacity.
    The velocity is determined by the expansion ratio, and the ratio of charge to bullet weight.

    My apologies for all the gobbley-gook, it's pretty complex. I guess the answer to your question should be "No, for typical rifle loads, the barrel length does not determine what the powder charge should be. In a typical rifle, changing the barrel length by a couple of inches will only change velocity by 20 or 30 fps."
  4. jrw1976

    jrw1976 New Member

    Mar 14, 2010
    Thanks that is the exact answer I was looking for.
  5. DGG!

    DGG! New Member

    Apr 6, 2010
    Here is a good article from the UK about the concept. The guy just started cutting inches off the barrel of .223 and .308 rifles and measureing the effect on velocity.

    I think it is also interesting to note his comments that the blast effect of the shots when up as the barrel length decreased.
  6. carver

    carver Moderator Supporting Member

    This whole thing is really kinda simple. It doesn't matter much what caliber you choose, there is a limit as to how much powder you can use. When the powder is ignited, and starts to push the bullet down the barrel, pressures build. This will limit the amount of powder you can use. To much, and you can blow up your gun, and maybe your self as well. All the longer barrel does is give the powder more time to burn. Burning all the powder gives you all the speed that load can give you. A shorter barrel simply does not always allow all the powder to burn. Thus, longer barrels usually give you more bullet speed. Hope this helps answer your question.
  7. DGG!

    DGG! New Member

    Apr 6, 2010
    Educate me a little.

    If barrel length doesn't really matter why did the militaries of the world stick with rifles/muskets with very long barrels for so long?

    Some of those old broomsticks were amazing long and I'm not sure what that got the shooter except a sore back lugging the damn thing around from battle to battle.

    I'm wondering if the longer barrel helped to stabilze the round and make it more accurate. Thoughts?
  8. Terry_P

    Terry_P New Member

    Mar 23, 2008
    The short answer is load up (according to the manuals) several 3 round test loads with precision and then see which fires best in your rifle. Once you find a powder that your rifle likes better then work different loads for that powder until you find one that gives you the best accuracy.
  9. carver

    carver Moderator Supporting Member

    There ya go, you answered your own question. The long barrels were necessary to stabilize the bullet. When rifling came along they just added riffling to the long barrels. Over time we found that with a good riffling, and modern components, we could shorten the barrels, and still achieve a decent load. Remember that Black Powder was a class A explosive. It all burnt at once. Our newer powders are classified as propellants, and burn much slower, by comparison. Longer barrels did not help with the speed of the projectile, just made it more accurate.
  10. LDBennett

    LDBennett Well-Known Member

    Dec 20, 2003
    Hesperia, CA
    Longer barrels remained when combat meant hand to hand, soldier to soldier fighting. The longer barrel, which had a baronet on it, gave the soldier a little more distance between him and his enemy. The soldier with the longer barrel may have had an advantage. Hand to hand fighting is all but over for the average soldier, except for the limited number of specially trained forces, so today the big fighting firearm is the short barreled carbine, like the M-4 or the AK series guns.

    When you compare the various wars and their tactics, from the Revolutionary War through WWI and WWII and on to the current fighting, you can see the barrel length necessities for each. Once hand to hand fighting was not the norm, the barrel lengths got shorter. Sometimes the men in control of firearms development were out of touch (old warriors) so the transitions were a lot slower than necessary. An example is how long the US semi-auto rifle was in development. Garand made a life's work out of that one gun. Look how long it took from conception to field issuance for the AR series of guns. That story is ripe with drama.

  11. Kevin Rohrer

    Kevin Rohrer Active Member Supporting Member

    Apr 9, 2010
    Medina, Ohio
  12. Tanker6

    Tanker6 New Member

    Mar 31, 2010
    Silsbee, Texas
    A bit off the topic, but just to add a bit to the development of military firearms started by LDBennett....

    Interestingly, many of the upper echelons of the military and government at the turn of the 1900's were concerned about the move from bolt action to semi-automatic rifles because they worried that the soldier would "use too much ammo." There was a mindset that each soldier should be a careful and precise marksman, and that the ability to shoot with each trigger pull would detract from marksmanship and create an ammunition distribution problem.

    As an example, look at the standard loads for cavalrymen fighting Indians in the late 1800's (each soldier normally carried only 40 rounds for his rifle) and the standard loads for today. I would never have dreamed of stepping outside the wire with only 40 rounds! :eek:

    Of course, as the calibers have decreased, so has the ability to carry more ammo. As a young and dumb M-60 gunner (waaaaay back when :D), I had 400 rounds belted up and loaded and carried another 400 in a bandolier. It seemed that I could never find that assistant gunner (who was supposed to be carrying most of the ammo) when I needed him. :rolleyes:

    It is interesting to study the development of tactics vs. weapons throughout the ages. The argument can often be made that tactics changed weapons, but as often, the opposite can also said to be true. A good example can be found in WW I. The development of the machinegun lead to the quagmire of trench warfare. However, trench warfare lead to the development of the tank (which, of course, is near and dear to this old tanker's heart :D).

    By the way (since I'm on a ramble anyways :p), the "tank" got it's name because during the secret development by the British, they told the welders and skilled laborers who were making the pieces of the first prototype tanks that they were assembling parts for a water tank to be used in the desert. :) Hence, "tank," which has stuck ever since.
Similar Threads
Forum Title Date
The Ammo & Reloading Forum Velocity vs Barrel Length for Handguns Dec 3, 2011
The Ammo & Reloading Forum 44 mag velocities and barrel lengths Dec 1, 2009
The Ammo & Reloading Forum Barrel Twist & Barrel Length Jul 8, 2008
The Ammo & Reloading Forum How do you remove a bullet stuck in barrell? Feb 17, 2016
The Ammo & Reloading Forum TC with 10" barrel .223 Dec 23, 2015