How HOT is a bullet in flight?

[kd7nqb]

Ok so we have all heard of the analogy of "filling somebody full of hot lead" but how hot are bullets when the leave the muzzle? What about at 10yds? 100yds?

I found this LINK http://rangerats.org/bullet.html which has one study but I would like to also explore the differences between bullet type as well.

Any ideas?

 

[Cannonball888]

I imagine not as hot as freshly spent brass as a bullet is air-cooling in flight. Freshly spent brass is pretty hot. Just ask the woman who caught one down her low-cut blouse and doing the jitterbug next to me at the indoor pistol range.

 

[chris in va]

If my calculations are right, a typical 9mm handgun bullet travels around 800mph, hardly fast enough to cause friction heat.

Now a rifle bullet runs about 2000mph and could certainly heat up some. Don't know if it would have enough time though.

 

[geronimo509]

I agree with cannonball, however I've been told that it really is a burning sensation when you get shot. Ps I told my girlfriend one time not to wear low cut shirts when we shoot, and showed her a pic of a scar from hot brass. she stays fully covered up when we shoot :banghead: lol its a good thing though

 

[LoneCoon]

Take the temperature of burning gunpowder, times the thermal constant of lead, times the time in contact with the burning gases, Minus the ambient temperature of the air, times the thermal constant of lead, times... something else.

I haven't got that far in my engineering studies, sorry.

 

[kirklandkie]

wow that's an interesting article, a 5.56mm is 513F when it leaves the barrel? let me see if i can do some calculations
assuming the outside temperature is 70F, like a nice spring day (we need surrounding environment temps to calculate a change in temp)
lets convert these to degrees C
Bullet(initial): 267.22C
Environment (static): 21.11C
delta Temp = 267.22-21.11C = 246.11C
the thermal conductivity of copper = 380 W/(m·K) (sure it's lead(going with the 193 round) core, but the outside is copper so we'll go with it)
surface area of a bullet = ...ok this gets impossible so we'll assume it's a perfect cylinder (which it obviously isn't) : (pi*(5.56mm/2)^2)+(2*pi*(5.56/2)*19.3mm)
= 361.4 mm^2
380*361.4*(246.11/distance between temps)
380*361.4*(246.11/0?)


AHHHH MATH....two problems here, first i've gone very wrong in my calculations. second i need the thermal conductivity of air and resistance and then we get into problems of the moving air over the bullet.
i'm still in school for engineering, sorry find a real engineer lol

-kirk

 

[Dynamite Rabbit]

Don't ignore the friction between the barrel and bullet -- I suspect that might be the biggest heat source.

 

[WardenWolf]

Depends on the range, the muzzle velocity, the barrel length, and many other things. Generally, though, a bullet would not be very hot. A bullet that's traveled 30 feet has probably dumped almost all of the heat it built up from the barrel from conduction with the air (note that convection is heat transfer to something else via heated air; in this case, it's being transferred from bullet to air via direct contact, and is thus conduction).

 

[Geno]

Here's a cool link: http://www.rangerats.org/bullet.html

We concluded that the bullet's temperature was around 267 degrees Celsius (513 degrees F). The bullet gets very hot as it is forced down the rifle barrel at supersonic speeds.

Geno
(Formerly Doc2005)

 

[ReadyontheRight]

I think the First Law of Thermodynamics says that the kinetic energy of the bullet's velocity turns into heat at impact. So it's hotter at impact than while flying through the air.

You could probably calculate the heat transfer based on feet per second and bullet mass. But it's been a loooong time for me since Chemistry and Physics.

To keep this thread politics related, the Second Law of Thermodynamics seems to be affecting our Constitution and Bill of Rights.

 

[Ratfood]

Don't ignore the friction between the barrel and bullet -- I suspect that might be the biggest heat source.

I think you nailed it

 

[benEzra]

A bullet that's traveled 30 feet has probably dumped almost all of the heat it built up from the barrel from conduction with the air

A rifle bullet is going fast enough to get hotter as it travels; frictional heating exceeds thermal losses until it slows down. So if it comes out of the barrel hot (which it does), it'll stay hot for a couple hundred yards, at least.

 

[The Lone Haranguer]

I am not able or willing to do the testing.

 

[PALMERJ]

Standing in the pits pulling targets one day at a 50 cal 1000yrd match I had a round go through the target bounce out of the burm and land near my feet. After marking my shooters target i reached down and burnt the crap out of two of my fingers. The projectile was a 800gr solid. I would think it was hotter then the piece of brass it came out of because I havent had fired brass burn like that.

Jon

 

[Mr.510]

Hot enough to light a cigarette!

http://www.youtube.com/watch?v=gDFL5_Jfhfc

 

[Jim Watson]

PalmerJ is correct. Even a .30 that bounces over the berm at 1000 yards is too hot to handle.

 

[Officers'Wife]

I imagine not as hot as freshly spent brass as a bullet is air-cooling in flight.

A projectile loses velocity pushing the air out of it's way as it travels downrange. This energy loss is converted to heat of which some will be absorbed by the projectile. Case in extreme- a meteorite entering earth's atmosphere will melt from the 'braking action' of the air rather than being cooled by said air.

 

[LibShooter]

I don't think a bullet would cool much in flight. It doesn't spend much time in the air. A short fat round like a .45 is nearly spherical, so does not have much surface area. (A rifle projectile would lose heat a litttle faster.) Also, lead is dense and can hold a lot of thermal energy. And has been mentioned, a bullet slowing from hundeds of fps to 0 fps inside the target converts all those ft-lbs into heat.

My uncle was shot while serving in Greenland with the Army Air Corps. He said the most intense sensation he felt was heat. He didn't know he'd been hit until the other MP (The shooter) ran to him, .45 in hand, sobbing "I'm Sorry!" My uncle said his first thought was "How did I get stung by a wasp above the freakin' Arctic Circle?"

An empty brass casing, however is a great radiator with thin metal walls and LOTS of surface. It would cool quickly.

 

[1858rem]

ooh how bout my 204 ruger at 4100fps? it already skins the critters an guts em'.....is it gonna cook the things for me too lol

there is another 20 cal made from a necked down 6mm ppc i think and has gotten high as 4800fps(wildcat round though)

 

[longdayjake]

I was involved in securing an emergency room when 3 police officers were shot in a shootout. I got to watch a surgeon examine bullet wounds. He said that if the bullet is not resting in an area that it can do future damage they generally leave it in there for 2 reasons. First, bullets get so hot that they are always steril when they go in and even if they pass through something that is not steril they are hot enough after they stop to completely cauderize the flesh surrounding the bullet wound. Second, bullets can safely travel to places that are not easy to get to surgically without causing more damage. They only remove them if they are in a dangerous area or they have to go and get other debris out near the bullet. (clothing, bone, other forms of shrapnel, etc.) Or if it is just under the surface of the skin.

I then watched him cut the bullet out of a cop's thigh because it was leaving a visible bump just under the skin. Turned out the cop that got shot by the bad guy started shooting back before he knew his buddies were already tackling the bad guy. Only one cop got shot by the bad guy and the other 2 got shot by another cop. Bad guy is dead though.

 

[noob_shooter]

pretty damn hot i bet.. haha

 

[kirklandkie]

ok second attempt:
55 grain 193 lead core bullet weighs: 3.6 grams = .0036 Kg
bullet speed leaving the chamber is: 938m/s
initial bullet temperature is: 267.22C
assuming the bullet is all lead (ignoring copper because it's a small amount of the weight) our specific heat is: 0.127 J/gm K
so we'll go about this by calculating the maximum temperature the bullet could achieve, aka hitting a solid object upon leaving the barrel:
Kinetic Energy = .5mv^2 = .5*0.0036*938^2 = 879,844 Joules

if:
Q = m * c * ΔT
where Q is the heat energy put into or taken out of the substance, m is the mass of the substance, c is the specific heat capacity, and ΔT is the temperature differential.

then: ΔT = Q / (m * c)
Change in Temperature = 879,844J / (0.127*.0036) = 1,924,418,197.73 Degrees Celsius is our maximum temperature of our bullet on impact?....but wait there's more!
add our initial temperature of 267.22 to the mix (now seems almost laughable)
we get:
1,924,418,464.95 Degrees Celsius!
In conclusion:
Thank god all of the energy of a bullet doesn't turn into heat when it impacts, because the lead would be instantly vaporized and you'd get lead poisoning in about a single bullet.
DOUBTERS TAKE NOTE: ok yes, this temperature is not realistic. However the calculations are sound i double checked, the difference is that the bullet often fragments and warps. If the bullet did not warp at all and stopped instantly then this would be the final temperature
it surprised even me

-Kirk

 

[heron]

the kinetic energy of the bullet's velocity turns into heat at impact.

I've seen this. A guy had a piece of Lexan sheet that he'd been shooting at, and hit with a .22, regular solid lead bullet. The heat from the impact softened the plastic as the bullet mushroomed out a little, and the plastic reformed somewhat around the bullet, encapsulating it. Same piece of plastic had a very shallow crater, about 3/4" in diameter, where he'd shot it with a .45ACP. That one scared him; the slug ricocheted back at his head.

 

[Dave/hoff]

KIRK! Shame on you! Surface area of the bullet is NOT impossible!
DO YOUR CALCULUS, ENGINEER!

 

[sharkhunter2018]

Sometime last year I shot a few rounds from various firearms, both pistol and rifle into a cardboard box that was full of magazines and phone books. I was trying to get an idea of HP expansion from a few handguns and tried a couple FMJs from a AK47 and 74 to see about penetration.

Bullets were recovered about within about 30 seconds after firing. Between the heat from firing, friction from the flight and friction of traveling through the magazines the bullets were pretty hot. Many were too hot upon recovery to hold and had to be juggled like a hot potato. Once in the open though, they cooled quickly enough to be held without juggling them between hands.