Barrel burners and velocity

Flyingbullseye

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    Quick question regarding barrel burner rounds. Its always said that the .243 or other 6mm variants will have for the most part the shortest barrel life with its high velocity. However the .223 never seems to be in that discussion, in fact in the caliber choices thread and others, its said to have a long barrel life but it also has a high velocity. How does the .223 with a velocity give or take 3100-3200fps good on the barrel but if shooting the heavier loads in the .243 at less velocity still causing a short barrel life? Nothing really against the .223 but just curious.

    Flyingbullseye
     

    Longshot38

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    Re: Barrel burners and velocity

    Barrel life has NOTHING to do with velocity. Heat is a barrel single worst enemy. Then you have to factor in powder charge, bore diameter, and pressure. All of those three factors directly relate to how much heat is generated.
     

    Massoud

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    Re: Barrel burners and velocity

    Barrel life is also affected by something called chambrage, which is what people are referring to when they mention an "overbore" cartridge. Chambrage is the relation of the chamber to the bore. Cartridges with a lot of chambrage, like a 6mm-284, create a lot of turbulence in the gases as they flow through the throat, this turbulence wears the throat much faster than normal.

    Another important factor in barrel wear is, in essence, inertia. This is when the bullet first engages the projectile, called engraving, the bullet is going from zero rotational momentum to suddenly spinning. This is the reason why gain twist barrels can extend barrel life. However, gain twist barrels are really only practical in projectiles with driving bands. I mean barrels with a lot of gain, not 14 twist to 13 twist. There is actually a formula for determining the optimal gain to smooth out the "torque curve" that is applied to the bullet.
    Justin
     

    Flyingbullseye

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    Re: Barrel burners and velocity

    Interesting, would have figured that a faster twist barrel would cause more friction shortening barrel life. Thanks.

    Flyingbullseye
     

    mheckman

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    Re: Barrel burners and velocity

    Specifically which 6mm cartridges, aside from the .243, give really short barrel life?
    I have a 6mm Dasher and it has really good barrel life.
     

    bohem

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    Re: Barrel burners and velocity

    6mm Rem, 6mm AI, 6mm Catbird (6mm-06 AI), 6mm Cobra (6-220 Swift AI)

    The 243 has a very short neck which contributes to nasty throat abuses. The 6mm Rem has a very long neck, more powder capacity and much longer barrel life when loaded to the same MV's.

    Barrel life does indeed have a factor with velocity, but it's far outweighed by the overbore ratio (chambrage? that's a new term for me) and the neck length. The powders used and the way that you shoot it has quite an effect too.
     

    cav has been

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    Re: Barrel burners and velocity

    <div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Massoud</div><div class="ubbcode-body">Barrel life is also affected by something called chambrage, which is what people are referring to when they mention an "overbore" cartridge. Chambrage is the relation of the chamber to the bore. Cartridges with a lot of chambrage, like a 6mm-284, create a lot of turbulence in the gases as they flow through the throat, this turbulence wears the throat much faster than normal.

    Another important factor in barrel wear is, in essence, inertia. This is when the bullet first engages the projectile, called engraving, the bullet is going from zero rotational momentum to suddenly spinning. This is the reason why gain twist barrels can extend barrel life. However, gain twist barrels are really only practical in projectiles with driving bands. I mean barrels with a lot of gain, not 14 twist to 13 twist. There is actually a formula for determining the optimal gain to smooth out the "torque curve" that is applied to the bullet.
    Justin
    </div></div>Justin, doesn't the shoulder angle and neck length affect the practical effects of "chambrage"?My understanding is that the combination of shoulder angle and the neck focus the flow of gasses more or less down the barrel, causing some combinations to more quickly erode the throat.
     

    DMann

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    Re: Barrel burners and velocity

    Not Justin, but yes - the short neck and a shoulder angle like that of the .243, combine in such a way as to focus the burning gases into the throat or leade of the barrel - like the nozzle of an acetylene torch. A more square shoulder and a longer neck keep more powder burning inside the case before it can hose the throat.

    For a really good compromise, look at the 6mm Super LR that Robert Whitley came up with at 6mmar.com.
     

    Massoud

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    Re: Barrel burners and velocity

    Yeah pretty much. Any change in geometry will have an effect, either positive or negative depending on the change. I've read, too, that the long neck will help but I don't have any first hand experience in that regard. This has, of course, been studied extensively by the .mil in regards to artillery/cannons and of course small arms.

    Another good example of the effect of turbulent gas in the bore is to look at a borescope pic of an autoloader with a gas port drilled into the barrel. Massive erosion can be seen in the gas port, counterintuitively, toward the muzzle side. Some rifles counter this with an angled gas port, which helps to stem the port erosion.