Powder & Short Barrels..

Discussion in 'Handloading and Reloading' started by RN, Oct 26, 2014.

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  1. rcmodel

    rcmodel Member in memoriam

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    Yes, apparently we are!

    rc
     
  2. JRH6856

    JRH6856 Member

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    Really? I thought forcing cone erosion was pretty much a fact of life in magnum revolvers.

    Whatever.

    Once the bullet has left the barrel, certainly there is more available O2 to burn the superheated gasses. More O2 is also available to complete the combustion of the remaining powder, some of which is still in the barrel, and some of which is expelled from the bore. Ask an ME about just what is involved in powder burns. It isn't just burning gasses, there are powder grains as well.

    Burn rate is just a relative indication of how fast a given powder formulation burns. It is not a representation of how fast the powder is consumed by combustion. This is because combustion takes place on the surface of the powder granule so the speed of combustion is affected by the ratio of surface area to volume. For example, for a given volume, a flat flake powder will have more surface area than a spherical ball powder or an extruded rod. Surface area of extruded powder can be increased by extruding the rod as a tube. A powder with a given burn rate extruded as a rod will be consumed slower than the same powder extruded as a tube, even though they burn at the same rate. And all powders are surface treated to control rate of ignition which also affects rate of consumption.

    Smokeless powder has a combustion curve. At the peak of the curve, the pressure is highest. Where this peak occurs in relation to the bullet's progress is where barrel length is important. If the peak occurs after the bullet has left the barrel, much of the powder's energy is wasted as a large part of the powder is till burning. So you want the peak to come while the bullet is still in the barrel. After the peak, pressure begins to fall as more of the powder completes its burn and less remains to to be burned. If combustion ends too soon, the bullet is driven by the expansion of existing gasses with no more conbustion to add more gasses to fill the expanding space. So, for full efficiency, you want a powder that peaks in time for 95-100% of the powder to be consumed by the time the bullet leaves the barrel.

    This does not even touch on the energy potential of the various powder formulation and is another determinant factor in how a powder performs.
     
  3. ljnowell

    ljnowell Member

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    I think one of the things that escapes most conversations is that people think that the powder burns from one granule to the next out the barrel.

    My statement above about 95% of powder was flawed in that I said burned, not burning or ignited. On a slow burning magnum powder many of the granules are going to ignite and still be burning as the exit the barrel. This is not indicative of wasted powder or powder blown out the end of the barrel and burned outside of it. This is simply powder with such a slow burn rate it's STILL giving off energy after leaving the barrel.

    The concept of 50% of the powder not burning until it's out of the barrel is false.
     
  4. JRH6856

    JRH6856 Member

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    I have no idea what point you are trying to make here. If any grains of powder are still burning when the bullet leaves the barrel, it is completely irrelevant whether they continue to burn inside the barrel or outside of the barrel. My point all along is that any powder that burns after the bullet has left the barrel will have no effect on the bullet once the bullet has left the barrel. Yes, it is still giving off energy, but for the purpose of propelling the bullet downrange, that energy is wasted.
     
  5. ljnowell

    ljnowell Member

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    If your point is powder burning after the billet leaves the barrel isn't pushing the bullet than your point is obvious and I don't see anyone disputing it.

    I clearly don't see what point you are trying to make here.
     
  6. Uniquedot

    Uniquedot Member

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    To my mind the point he is trying to make is to choose a powder suitable to the cartridge and firearm that gives best velocity while wasting less energy and allows the shooter to have less muzzle flash to deal with...of course this Is my thinking on it and as usual I could bee wrong.
     
  7. ljnowell

    ljnowell Member

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    Best velocity will always be from the slowest powders which you are claiming are wasteful.

    This is no more than a matter of opinion. If you don't like muzzle flash and don't care about losing velocity then use a faster powder but you will not be getting the best performance from it b
     
  8. Uniquedot

    Uniquedot Member

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    Naturally when you have the barrel length to allow complete internal combustion, but say what about a snubbie? Lots of info in shotshells manuals on this stuff. Why is it so much different in a handgun? There is also diminishing returns to worry about in long barrels. I'd personally like to see some more scientific research on short barrels and powder burn rate. I suppose in the meantime we can just take the powder companies word for it.
     
  9. JRH6856

    JRH6856 Member

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    That is just not so. Sometimes it is true, sometimes it is not. Best velocity is produced by the powder that produces the best velocity regardless of wheter it is fast or slow. And depending on the load and the gun, it may be either.

    Look at the following two load for .380ACP in a Ruger LCP:

    15 Vihtavuori N330 4.3g 965fps 18813psi 91.9%burn
    17 Alliant BE-86 4.8g 965fps 18813psi 77.9%burn

    Almost identical burn rate (17 and 15) produce the same velocity and pressure, but the N330 load does it with less powder weight because more of it is consumed in driving the bullet.

    OTOH, an even slower burning powder gives this:

    18 Alliant POWER PISTOL 5.5g 949fps 18813psi 62.4% burn

    Same pressure, but lower velocity, from more powder because 37% is still unconsumed when the bullet leaves the muzzle.
     
  10. ljnowell

    ljnowell Member

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    Yes, it is so. The powder that gives the best velocity from a six inch will give the best velocity from a two inch barrel. No matter what your software says there are years of tests to back up this very true fact.

    Using a powder that is not proper for a loading will give you less velocity that's a given and doesn't prove anything outside of the fact that you can take a statement out of context.

    Slowest powder appropriate, there is that better? Of course if you take a slower powder that is a mismatch for the load it will underperform. No one has argued that either. I'm not sure what your real point is but you surely aren't making it.
     
  11. ljnowell

    ljnowell Member

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    The short barrel snubbie is not a shotgun. It seems pretty simple to understand.

    Again, my statement is simple "the powder delivering the most velocity from a 6 inch barrel will deliver the most from a 2 or 3 inch also."
     
  12. JRH6856

    JRH6856 Member

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    I'm not disagreeing with that, nor does my software or my experience.

    I'm just trying to determine what your context is here. My point is that there are more accurate ways of of estimating what happens when powder burns than numbers pulled from nowhere.
     
  13. ljnowell

    ljnowell Member

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    Good lord man that was ten posts or more ago! I told you it was a made up number! The discussion is about choosing powder based upon barrel length. Barrel length isn't the issue, it's the desired velocity. That was the whole point before you started posting quick load ESTIMATES, not fact, estimate.
     
  14. ArchAngelCD

    ArchAngelCD Member

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    It is a fact the powder that delivers the highest velocity in a 6" barrel will do the same in a 3" barrel too.

    The reason you see a muzzle flash with a handgun powder is, when the bullet leaves the barrel and exposes the hot gasses to a new source of oxygen the gasses reignite. Smokeless powder supplies it's own oxidizer and once it's gone it doesn't matter how long the barrel is, the gasses stop burning until a secondary source of oxygen is available. (like when the bullet leaves the barrel and exposes the gasses to the air) Those gasses will reignite with any length barrel but with the longer barrel the shooter doesn't notice as much as with a shorter barrel.

    Why does this topic always cause arguments especially when most of the information being given is misinterpreted?
     
  15. Jim Watson

    Jim Watson Member

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    There is a comfort factor, though.
    Mason Williams - the gunzine writer, not the musician - did a piece on the 2" .357 Magnum.
    He found, as anybody can, that the slow burning powders that gave highest velocity in long barrels, also did in short barrels. But that blast and recoil were annoying. He tried this and that powder available at the time and settled on Blue Dot instead of the usual 2400. It did not give as high velocity as 2400 but the blast was relatively much less.
     
  16. JRH6856

    JRH6856 Member

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    Perhaps because it is often misstated (at least it appears so to the reader) which is probably why it is misinterpreted.

    Like your statement that muzzle flash is due to gasses reigniting. Yes, in some cases, but it is also due to powder that is still burning when the bullet leaves the barrel. I don't know why it is so hard for people to understand that 100% consumption before bullet exit is not the norm.
     
  17. ljnowell

    ljnowell Member

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    I have not seen a single person say 100% burn prior to the bullet exiting is the norm. Not a single post.
     
  18. JRH6856

    JRH6856 Member

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    I believe that is clearly implied in post 24 and agreed with (by you) in post 25. And I say "clearly implied" because it was clearly stated by the same person in another thread.
     
  19. ArchAngelCD

    ArchAngelCD Member

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    There is a difference between a powder being 100% used up and no longer burning. Like I said above, once the oxidizer is used up the hot gasses stop burning. The gasses reignite when a new source of oxygen is added, the fresh air.
     
  20. JRH6856

    JRH6856 Member

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    I'm not sure what you are trying to say here. Rather than me misinterpreting it, could you explain in a little more detail?
     
  21. murf

    murf Member

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    have any of you sat around a campfire and watched the flames dancing up from the burning embers? any of you want to tell me what part of that flame is unburned wood?

    hot combustion byproducts show color. cooled down combustion byproducts don't show color (unless normally colored).

    grab a speer reloading manual # 14. go to pages 877 and 878. compare the load charts and then lets continue this discussion.

    just trying to get some solid data here to try and get rid of all the wags floating around here.

    slow-burning powders can be loaded faster than fast-burning powders regardless of barrel length. loading manual data bears this out.

    murf
     
  22. ljnowell

    ljnowell Member

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    I believe you are clearly mistaken. If you attempt to apply meaning to my words that was not intended you may come to an improper conclusion.

    I was merely stating what contributes to muzzle flash.
     
  23. JRH6856

    JRH6856 Member

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    The sparks. Same with muzzle flash.

    I'm sorry, but what does that mean?
     
    Last edited: Oct 30, 2014
  24. JRH6856

    JRH6856 Member

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    If you do not clearly state what you mean, incorrect inference is a risk you take. I can't read your mind, only your words.

    I think we have spent enough time arguing past each other to no useful purpose. I'll stop if you will.
     
  25. ljnowell

    ljnowell Member

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    Agreed. We surely aren't getting anywhere, are we?
     
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