What's the temperature of a fired bullet?

[41mag]

& 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?

 

[R.H. Lee]

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?

 

[pignock]

RileyMc asked:

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?

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.

Keith

 

[Boats]

Too hot to catch that's for sure.

 

[P95Carry]

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

 

[fletcher]

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.

 

[RON in PA]

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.

 

[DRZinn]

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

 

[Stickjockey]

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.

 

[41mag]

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?

 

[fletcher]

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

 

[jsalcedo]

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.

 

[HKrazy]

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

Full Automatic Fire Issues:
Suppressors shown with or designed for machine guns are rated for fully automatic fire. In the case of suppressors designed for .223 (5.56mm), there are some limitations in the duration of fully automatic fire due to shortcomings in the ammunition, not the suppressor. 5.56mm is a unique cartridge. The projectile is physically small and lightweight. The relatively high muzzle velocity causes excessive barrel heating from friction, with outside barrel temperatures exceeding 700° F in a 100 round burst. Bore temperature is considerably higher. The projectile contains a small quantity of lead, which after a 90 round burst starts to soften and/or melt. The softening of the lead core results in geometric instability of the projectile, causing excessive yawing, tumbling, and suppressor baffle contact. These effects are not normally seen anywhere near this early in larger caliber projectiles, such as 7.62 NATO. Although the suppressor is capable of withstanding long bursts using ammunition not containing any lead, any lead containing 5.56mm ammunition will damage the suppressor. Because of the deleterious heating effect, most weapon manufacturers place serious limitations on sustained fully automatic fire and state that the barrel is ruined after a 200 round burst.

LINK.

 

[carebear]

<tough guy mode>

All mine end up at 98.6.....

At least for a while.

</tough guy mode>

 

[41mag]

WOW!Thanks HKrazy.

200 round burst & then it's scrap!

 

[P95Carry]

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.

Ever pick up a freshly fired bullet?

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.

 

[Glock19Fan]

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.

 

[P95Carry]

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.

 

[Monkeyleg]

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.

 

[Sleeping Dog]

The bullet cauterized the wound channel

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

Regards.

 

[Sleeping Dog]

Apologies for using the word "doofus". I realize personal attacks are not polite or helpful.

Again, apologies to any of you nine-toed fast-draw artists.

Regards.

 

[41mag]

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.

Well,that seems to me to lead to another Q.

Consider calibers like 50BMG,338Lapua,heck even a 168grn .7.62x51 fired to targets at 1000M.Thev've got the flight time & IIRC the first two are still supersonic @ that range.

Does anyone else wonder if these first get hot from the propellant & bore friction,maybe cool off in the first couple of hundred feet & then heat up again as they absorb the friction heat from the long flight?

 

[P95Carry]

I know one thing Monkeyleg ... however wrong I may be in my assessment of bullet temp' - and I only theorize ... I shall resist the ultimate test - of shooting into any part of my anatomy!!!

Tho it might be only way to find out for sure!

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

maybe cool off in the first couple of hundred feet & then heat up again as they absorb the friction heat from the long flight?

I was considering this aspect and yeah I guess marginall cooling followed by air friction heating ... but even so - time to target is gonna be not a huge lot over 1 second at the long range ... enough I wonder to really get the heat into the core?? Still not sure.

I guess there is probably some definitive test info out there somewhere - I am probably way off base without realizing - all theory and no proof!! .

 

[Selfdfenz]

I googled up a pdf from a company that does infrared temperature measurment and in their test a 223 bullet printed at 267 degrees.

S-

 

[P95Carry]

Self' ... wonder at what point that was in flight.? However - time for me to eat humble pie as - I was most assuredly - WRONG - that's another screwed-up theory makes it to the trash!!