What's the temperature of a fired bullet?

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P95,

It was a lab test so I thinking it was a few feet at most. So I'm thinking when we are talking 267 degrees that is how hot the bullet is near the start of its flight.

The thing I really wonder about is "how much does the thing cool off in flight".
Assuming large caliber bullets have more mass they would cool more slowly than small ones, however but the thing is in flight such a short time, it can't cool much.

After all, being bullets one would think all the suff that makes them ballistically efficient and reduces drag also keeps the air from being a real wonderful heat sink.

Not being an engineer makes my head hurt to think about this stuff!

S-
 
Self' ... ah, pretty early on then - much as I imagined.

As for cooling in flight - I'd think we have a parallel to heat gain thru air friction, in a sense.

Basically, the time frame for loss or gain is so short. A small bullet having less mass will heat or cool faster - but OTOH it's surface area is smaller.... so that can affect temp loss or gain. At other extreme, a .50 cal has way more mass - and so IMO less likely to heat or cool as fast, but - it does have a greater surface area!

I am way too lazy to do the math here but there is, will be, a fairly easily derived math expression for caliber, length, density, temp coefficient etc ... such that we could probably derive a constant, or a definitive relationship of the variables.

I do tho still reckon heat gained... from powder combustion, will be perhaps seemingly quite modest - most just at base - but pretty sure the friction thru rifling engagement will be well significant. Interesting here tho is the fact that bullet surface temp might be high (jacket and outer core) ... but would not be at all surprised if at that early stage, bullet lead innermost core still almost cool.
 
"I do tho still reckon heat gained... from powder combustion, will be perhaps seemingly quite modest - most just at base - but pretty sure the friction thru rifling engagement will be well significant. Interesting here tho is the fact that bullet surface temp might be high (jacket and outer core) ... but would not be at all surprised if at that early stage, bullet lead innermost core still almost cool."

Friction from passing thru the barrel as the main heat source makes absolute sense to me. I hadn't thought about air friction as a heat source but at MACH 2+ thru MACH 3+ or so I bet it sure is.

S-
 
Now that I think of it...what makes the tracer round start tracing, the fact that it passed thru a ball of fire when it left the muzzle or the fact it got so hot on its way down the barrel? Having never been in the military I never had the benefit of an explanation but I'm thinking the latter.
Wonder what the ignition temp for tracer material is?

S-
 
No idea for specific ignition temp for tracer material but - believe that the powder burn flame front is all that is needed, on bullet base. Many incendiary tracer compositions tho do have a finite ''start-up'' time, meaning that visible trace may only be properly visible some 100 yds down range, and beyond, after fully ignited.
 
Think a minute. If the friction in the barrel plus the temperature of the gas were enough to melt the bullet, no bullet would ever leave the barrel; only a blob of molten metal would come out. Yes, high temperatures can erode the base of a lead bullet enough to require gas checks to be used, but I have recovered dozens (if not hundreds) of bullets that had no sign of any melting of the lead or the core of a jacketed bullet.

Don't get confused by the melting of bullets which strike a steel plate or a rock. When that happens, all the bullet's kinetic energy is converted to heat in an instant; it is that heat that melts the bullet, not the heat from firing the bullet, which has long since dissipated.

FYI, that is the way AP ammunition works. The bullet strikes the plate, its energy is converted to heat so the bullet jacket and the surface of the plate melt, allowing the AP core to go through the molten plate. If the plate is thick enough that the heat is absorbed too fast, the AP core will not penetrate, but will stick in the plate when the molten part solidifies.

Jim
 
temperature is not really going to be an issue as far as it affecting the target. The residance time in the barrell is very short (for a 300fps bullet about 0.0013 s) even though the gasses are 1500-2000f, that is not enough time to significantly raise the temperature of the bullet, some frictional heating will also occor, but the bullet being made of lead is dense and heave and not enough energy can be transfered to it to raise the average temperature. for a 200 yard shot the 3000fps bullet will be in flight for roughly 0.2 seconds. During that time the heating that did occur in the barrel is being conducted to the center of the bullet. It does take time for the heat to travel from the surface of the bullet to the center of the bullet. The sides of the bullet may be cooled by the convection of the flying projectile. there is the possiblitly of the tip heating up if the bullet is fast enough, at 3000fps the air temperature that the bullet tip sees is going to be roughly 800F. This is the stagnation temperature of air at 300fps. Again this flight tiem is quite short. not enough time to really heat the bullet. once the bullet strikes flesh it is rapidly cooled as it contacts a liquid media that is able to efficiently convect heat away from the bullet.
 
Armor piercing shaped charges (RPG) penetrate by melting a hole with the shaped charge, but I don't think that regular small arms rounds do. I may be wrong, but armor piercing rounds go through more than steel, and they don't likely melt through concrete or other materials. The cores are very hard, and resist deformation upon impact. I believe the jacket and lead part strip away as they deform upon impact, they are simply a vehicle to deliver the core through the barrel and to the target.

I've also picket up freshly fired bullets, they are HOT when fresh.

I recall hearing people say that the sensation they felt when shot was "DANG that BURNS!!!"
 
Remember Myth Busters Ice Bullet? The ice didn't meld during firing, but it lacked the mass needed to do any real damage. I'd guess based on what I saw there that the bullet doesn't have time for good heat exchange under most circumstances. Although, the full auto/silencer info was interesting. Sounds like a liquid core projectile would have some interesting characteristics.
 
Another factor to consider is--how hot does the brass get? The brass is subject to the same burnings (maybe more, since it stays put while the bullet is moving.) OTOH, the brass does't pick up heat from friction.

I don't understand all these stories about getting burned from brass. When I shoot my .308 or my .223 or my 7.5 Swiss, I catch the brass in the air when I eject it. That is usually within 1 sec of firing, and it doesn't have much time in the air to cool. The brass is warm, but not too hot to hold.

Pistol brass? I dunno. I've never been able to catch pistol brass in the air. Been hit by some, and it didn't feel hot. But maybe I wasn't is contact with it enough for thermal transfer.

So my point is, if the brass doesn't get all that hot, how does the bullet get very much hotter?
 
Dave,

"I don't understand all these stories about getting burned from brass. When I shoot my .308 or my .223 or my 7.5 Swiss, "I catch the brass in the air when I eject it. That is usually within 1 sec of firing, and it doesn't have much time in the air to cool. The brass is warm, but not too hot to hold."

This may have nothing to do with anything but I have noticed may times HP cases are not beyond being handled after firing....... but let a 22 case from one of the botton ejecting Browning 22 autos get caught between your shirt sleeve and skin and it will "fry" to your skin. Don't ask me how I discovered that, over and over again. :D

S-
 
I remember getting struck in the leg by a ricochet from my .22lr (it just bounced off my leg), that bullet was, I'd guess 150 degrees, but since lead doesn't hold heat energy very well, it didn't feel too hot, unlike 150 degree water.
 
Not so fast...

  • Is that a European bullet or an African bullet?
  • Laden or unladen?
  • Is it carrying a coconut?

- 0 -
 
Remember Myth Busters Ice Bullet? The ice didn't meld during firing, but it lacked the mass needed to do any real damage.
Click to expand...

IIRC, the ice bullet never left the barrel intact - it kept shattering before leaving. As soon as it hit the rifling, it probably shattered - ice is not flexible enough to take the indentions rifling would put on a real bullet. The mass of an ice bullet would have the mass to do damage, IF it could stay intact, but it couldn't.
 
DaveR?I have had burns from both 40S&W & 22lr fired from pistols.

A .40 was caught between my glasses my head.The .22 landed on top of my T-shirt collar.

Had a burn scar for months.
 
I, too, have been burned by cases.

My most memorable was when I was bench shooting my .22LR Marlin 60. The shooting range has individual stalls, with the walls being about 4 feet apart. One of the ejected cases bounced off the wall, and landed on my left arm, just below the inside of my elbow, and rested there for a second or two until I brushed it off. It burned into the skin. This was around a year ago and the scar is still visible.

Ive been hit by hot cases from my Glock 19 but non of them were as bad as the little .22LR.

I guess the outside of the case of the thin .22LR heats up a lot quicker than the thicker cases of the .308. I probably could catch a .22LR after being fired without being burned, but it would be tricky. :uhoh:
 
As Far As I Know

Assuming a lead bullet:
c(p) about 129 J/(kg-K)
k(bullet) about 35.3 W/(m-K)
h(air) = 500 W/(m^2-K)

Temp(bullet) = T(air) + (Temp(initially) - T(air)) * e^(-h*Area*time/(bullet mass*c(p)))
or​
T(f) = T(air) + [T(i) - T(air)] * e^(-h*A*t/(m*c(p)))

The air temperature (recompression shock region) is probably going to heat the bullet up significantly along with the air friction :fire: .

A spherical, lead bullet with a .003 meter radius, an initial temperature (temperature from the barrel) of 400K (127 Celsius), flying for about 10 seconds in air that is heated to about 700K (427 Celsius) will have a final temp of 572K (about 300 Celsius :eek: ).

But if you want to know how hot the bullet really is experimentation is the cheapest way to go.

-David
 
Steel Plate

.
Jim is correct about bullets being hot after hitting steel. The heat softens the steel and allows the bullet to penetrate. I am not sure, but I think certain steel is hardened by high temperatures thus making it acceptable to shoot with rifles and not divot it since the steel can withstand the heat.
 
Load a 40-50 grain varmint bullet over a strong powder load in a 223 and the bullet can vaporize. Done it many times. I don't know where the bullet goes but you can get a smoke trail where it was and nothing hits the target. We were using a Remington XP100 action.
 
I'm not sure the numbers given to us by that infra-red lab test will be terribly accurate; they probably took the measurment a few yards from the muzzle, at which distance the bullet would have been unevenly heated (hot jacket, cool core).

...and isn't the "exploding varmit bullet" simply the bullet coming appart under centrifugal forces?
 
Load a 40-50 grain varmint bullet over a strong powder load in a 223 and the bullet can vaporize. Done it many times. I don't know where the bullet goes but you can get a smoke trail where it was and nothing hits the target. We were using a Remington XP100 action.
Click to expand...

That's usually the result of a weakly constructed bullet being spun too fast by the rifling. The bullet can't handle the centrifugal force and bursts shortly after leaving the barrel.
 
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