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What's the temperature of a fired bullet?

Discussion in 'General Gun Discussions' started by 41mag, Feb 21, 2005.

  1. 41mag

    41mag Well-Known Member

    & how much heat energy is lost in flight?

    Say you had two fmj rounds.One a .357mag & the other a 7.62x51.

    How hot is the bullets surface as it leaves the muzzle,& how does air friction affect its cooling?

    &,if they are hot,why don't bullet holes cauterize themselves?
    Last edited: Feb 21, 2005
  2. R.H. Lee

    R.H. Lee Well-Known Member

    That's a good question. Since a cast lead rifle bullet needs to be gaschecked the temperature is apparently enough to melt lead. How hot is that?
  3. pignock

    pignock Well-Known Member

    RileyMc asked:
    The gas check keeps the combustion gasses from eroding the base of the bullet and leaving lead deposits in the barrel.

    I don't use a thermometer when I cast but as near as I can remember, the melting temperature for unalloyed lead is somewhere around 600 to 700 degrees F.

    The bullets, in the internal ballistics phase of projection, stay below this. I would guesstheir temp would not exceed half the melting temp.

  4. Boats

    Boats member

    Too hot to catch that's for sure. ;)
  5. P95Carry

    P95Carry Moderator Emeritus

    The one thing I think here is, the thermal coefficient of lead is low ... copper of course way higher. but, the very brief exposure to the - admittedly - very high flame temp at combustion time, will not IMO give enough ''time envelope'' to markedly allow for much temp gain.

    The gas check deal - that is very much just taking care of bullet base ... a very thin section that might be softened - the remaining bullet mass will have inadequate time to conduct much. Some heat will be present I'd guess from friction too - but all this will hardly yield a significantly ''hot'' bullet. Warm probably at best.

    Only my own 2c
  6. fletcher

    fletcher Well-Known Member

    Yes, I can guarantee those gases are way over the melting temperature. However, as P95 said, there is not enough time for the heat to transfer far into the bullet. The simple fact that some of the lead on the back vaporizes shows that the temperature definitely exceeds the melting point. The bullet probably gains the vast majority of its thermal energy from friction with the barrel. And I imagine the bullet cools down relatively quickly once it leaves the barrel.
  7. RON in PA

    RON in PA Well-Known Member

    Since bullets are extruded through the bore I suspect that any temperature rise would be a combination of friction as well as the heat from the propellent combustion.
  8. DRZinn

    DRZinn Well-Known Member

    Even if the bullet didn't cool in flight, it wouldn't be in contact with the skin long enough to cauterize anything.
  9. Stickjockey

    Stickjockey Well-Known Member

    Temperature aside, I'd guess the reason for bullets not cauterizing the wound has something to do with the combination of the bullet not being in contact with the tissue for a long enough time and the inherently dynamic nature of terminal ballistics.
  10. 41mag

    41mag Well-Known Member

    O.K.,so the bullet gets a little from the propellant & a little from the bore.

    What about the air as it flies through it?
  11. fletcher

    fletcher Well-Known Member

    It probably gets most of its heat from the bore, but in flight, most likely loses nearly all of that heat in flight.
  12. jsalcedo

    jsalcedo Well-Known Member

    Ever pick up a freshly fired bullet?

    It is hot enough to have to toss it from hand to hand while it cools.

    I would say for example a FMJ .45acp bullet temp would be around 160 degrees about 8 seconds after firing.

    This is from me retrieving bullets that bounced off of target stands and steel plates. Not sure if the quick deformation adds heat.

    I'm not sure if rifle bullets would be hotter or cooler.
  13. HKrazy

    HKrazy Well-Known Member

    I don't have all the answers to your questions but this info from Gem-Tech's web site might interest you:

  14. carebear

    carebear Well-Known Member

    <tough guy mode>

    All mine end up at 98.6.....

    At least for a while. ;)

    </tough guy mode>
  15. 41mag

    41mag Well-Known Member

    WOW!Thanks HKrazy.

    200 round burst & then it's scrap!
  16. P95Carry

    P95Carry Moderator Emeritus

    I can certainly see sustained full auto becoming a problem - always wonder how GE mini-gun manages, even tho 6 barrels and some cooling time between each barrel's cycling.
    I agree, a retrieved bullet can be quite hot. I tend to imagine much of that tho is by heat generated thru deformation.

    I recall shooting an old gearbox ... still containing oil ... an old .303 milsurp penertrated the cast case easily and after that a very noticeable amount of smoke exited the hole! Seemed probably that the bullet had absorbed a considerable portion of the energy expended in punching thru, by deformation - and so darned hot.
  17. Glock19Fan

    Glock19Fan Well-Known Member

    I would guess the bullet would be almost as hot as the shell casing. Although the burning gun powder only reaches the base of the bullet, the friction from the bore and air will heat up it signifcantly as mentioned.

    I remember hearing about supersonic airplanes having problems with their skins overheating from the friction from air alone, and IIRC, the temp was around 600 degress F. I think it would react the same with bullets.
  18. P95Carry

    P95Carry Moderator Emeritus

    Glock - the shell casing, being the primary containment for the combustion - and being brass which has quite a high thermal coefficient .... will get hot real easy.... and it is subjected to the temperature for a significant time, being the ''backstop'' against the bolt for the duration.

    I have considered further re friction - and would venture to suggest that HV bullets, tavelling a long barrel will in fact probably get more than warm ... different from handgun situations.

    Whilst the supersonic skin heating phenomenon is a fact - I'd think that ''flight time'' for the bullet - measured in fractions of a second for most part - would not allow for a great heat input - the copper jacket would heat quickest of course but the lead core would IMO still be lagging well behind on heat absorbtion.
  19. Monkeyleg

    Monkeyleg Well-Known Member

    We had a guy at a local indoor range shoot himself in the leg a few years ago. He was drawing from a holster and snagged the trigger somehow.

    The bullet cauterized the wound channel. There was no blood.
  20. Sleeping Dog

    Sleeping Dog Well-Known Member

    Maybe the muzzle flash and burning trousers cauterized the wound. No blood? Maybe all the blood was in his face from embarassment. :)

    Two words come to mind: Ouch, and Doofus


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