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Of these things, what causes the most heat in a barrel?

Discussion in 'Rifle Country' started by brentn, Nov 1, 2007.

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  1. brentn

    brentn Member

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    Just curious, but

    Is it the ignited gunpowder?
    or
    Is it the friction from the bullet moving down the barrel?
    or

    Are they equally responsible for the heat caused? Is one more than another?
     
  2. JesseL

    JesseL Member

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    I'm pretty sure most of the heat is from the burning powder.

    In gas operated guns, the gas system gets hot pretty quick without ever touching the bullet, and firing rounds that should have relatively little bore friction (ie sabots) still tends to heat up the barrel too.
     
  3. Slugless

    Slugless Member

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  4. MrBorland

    MrBorland Moderator

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    The scientific way to look into this would be to fire a round that contains no powder and note any difference in barrel temp. Fortunately, the Aquila Colibri .22 rimfire is such a round. It contains only primer, and a shoots a 20grain bullet at around 350fps*, so with an appropriate backstop, you can practice with your revolver in your garage. Anyway, after shooting a cylinder full of these out of my S&W, the empty cases, let alone the barrel, aren't even warm, so I'm gonna go with the burning of the powder as responsible for the heat.

    *yeah, yeah - before I get flamed - I know - the slower bullet also produces less heat-producing friction, so I'm changing 2 variables.
     
  5. duck911

    duck911 Member

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    By leaps and bounds, the powder.
     
  6. jpwilly

    jpwilly Member

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    burning powder = heat = air pressure/expansion...
     
  7. Outlaws

    Outlaws Member

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    Powder. If you put more powder (220Swift) down the same diameter hole (223REM) you will burn out the barrel faster. Its not the speed of the bullet.
     
  8. rcmodel

    rcmodel Member in memoriam

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    Source = Hatcher's Notebook
    Army ordinance tests of a 30-06 in a BAR found that only 29 1/4% of the powders energy is transfered to the bullet.

    The other 70 3/4% is heat loss.

    Broken down:
    Heat to brass case = 131.0 calories.
    Kinetic energy to bullet = 885.3 calories.
    Kinetic energy to gases = 569.1 calories.
    Heat to gun barrel = 679.9 calories.
    Heat in exhausted gases = 598.6 calories.
    Total from powder charge & primer = 2,864.0 calories.

    Additional heat generated by bullet friction = 212.0 calories.
    Total of one shot of 30-06 ammo = 3,076 calories.

    [​IMG]
    rcmodel
     
  9. benEzra

    benEzra Moderator Emeritus

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    The gas behind the bullet (assuming a rifle bullet here) starts out in excess of 1000 degrees and 50,000 psi. A lot of that heat will end up transferred to the barrel.
     
  10. jpwilly

    jpwilly Member

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    Sounds like we need more energy efficient rifles...we'll have to put some genius to work on this.
     
  11. JesseL

    JesseL Member

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    We know how to make them more efficient, but who wants a rifle with a 6-foot barrel?:neener:

    Really though, this is one of the reasons for the newer generation of short cartridges. Smaller charges of faster power in small cases and higher pressures=a little better efficiency for a given barrel length.
     
  12. kymarkh

    kymarkh Member

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    With all those burnt calories I should be skinnier than olive oyl...
     
  13. jacobhh

    jacobhh Member

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    Any barell material that is an insulator such as fiber, ceramic etc.
    and not a huge metal heat sink would be more efficient as long as
    it lasted but a shorter lifespan and higher initial energy expended
    equals a net loss. Ongoing research.

    Sure will make for some interesting load data.
     
  14. Hunter0924

    Hunter0924 Member

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    From my understanding the bullet friction to the bore is what is responsible for most of the heat.
    Think about how much time the deflagrating powder spends in the bore compared to the amount of friction of swagging copper into the rifling.
     
  15. P-32

    P-32 Member

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    Hunter, next time you go shooting, stand next to your buddy and catch a piece of brass fired out of an auto loader go down your shirt. Then report back on where the heat comes from.
     
  16. rangerruck

    rangerruck Member

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    powder all the way. Look at the new custom shop 5-35c cart, made up with Savage. They use a superfat cart, with concave shoulders, and a long neck, also uses proprietary powder mix. this round uses about 20 % less powder than a 223, and yet moves a 35 grain bullet about 4800 fps. with it's super long neck, the powder plug, as it moves, is rebounded into by pressure, then moves up the blast column of the case, gets hotter, and hotter. As it begins to get into the shoulder/neck area, it us superhot, but the plug is almost completely burned up. By the time it gets into the neck of the cart., it is now burning out, and the brass of the neck swallows up the excess heat rapidly, then displaces it. this cart., shows excellent throat wear/ bbl life.
     
  17. slzy

    slzy Member

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    heh,heh,heh,P32,happened once and i buttoned up all the way.
     
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