Home Forums Hunting & Shooting Ask The Gunwriters Temperature of Fired Bullet

Even an ambient temp bullet would produce enough friction in the brief time it takes to push through flesh to feel hot. I suspect the heat of the bullet increases as it expands inside of flesh and bone. Even so, I have yet to recover a bullet in meat which had the slightest evidence of being even remotely cooked.

This is not correct, it has the relevance of being the correct rotation rate. A rate is per time, not per distance and has nothing to do with the total number of rotations before impact.

One example of its relevance would be in the calculation of rotational forces at the jacket of the bullet.

Such forces would be much higher on a bullet of a given diameter fired at 3,000 ft/s versus 800 ft/s, for instance.

Yes and the sun also rises-- its not relevant within the context of the question- does rotational kinematics effect bullet segmentation? No doubt that many algebraic relationships exist, and if the stated figure were meaningful to a model relating the two but it doesn't. The time and space constants can be ignored in calculating other larger forces at work. Since were on if's-- if the flight time was 1/60 of a sec. the rotation would be 5400 rps, and for 1 min. the rpm would be around 300000. Ee know the axioms of distributive algebras still work.

The infinitesimal duration of a bullet's flight is nothing compared to the long duration of the SR-71's flight. Surely, the friction of flight takes a while to heat the moving object. How much heat can friction with air impart to a bullet within at most a couple of seconds?

So true, and to add to that a bullet is not an airfoil, it does not fly, it is projected.

This thread makes my head hurt

Interesting tho...

It is not true that a bullet with a 1-12" twist will rotate one turn per foot of travel regardless of forward speed. A bullet's forward feet per second decreases rapidly due to air friction, but its rotational speed hardly decreases at all. Therefore, as its forward speed decreases, it will spin more than one turn per foot of travel even though its rpm remains the same. If it were somehow to come to a dead stop in midair, it would still be spinning at that same incredible rpm.

Wow! I've stirred up some very interesting hornets' nests with my question. Here's another one:

Let's say I've reloaded two .30 caliber cartridges to fire in the same rifle. All the components are the same except for the powder charges. (The rifle has a 1-in-12 twist rate.)

The first cartridge will fire the bullet at 1,800 fps. The second cartridge will fire the bullet at 3,000 fps.

Okay, since the rifle has a 1-in-12 twist, are both bullets only turning once every twelve inches? To me it seems the faster the bullet is expelled the more momentum and more rpm's the bullet would have once it leaves the barrel.

I've got to lay down and put an icepack on my head now!

It is not true that a bullet with a 1-12" twist will rotate one turn per foot of travel regardless of forward speed. A bullet's forward feet per second decreases rapidly due to air friction, but its rotational speed hardly decreases at all

That is correct, but only noticably at extended ranges, also the the rate of spin slows slightly if you want complete info. although the differential rate of change is significantly less. the point was to put the forward amount of travel in perspective to the rotation. The stated rpm figures give the illusion the bullet comes out of the barrel spinning at some incredible rate. If you recall several years ago some of the ads for some bullets were advertising a buzz saw effect which made their bullets better. The amount of force generated by the spinning is also related to the dia. of the bullet.

yes, but the faster velocity will have a shorter time frame.

That's what he just said. I believe you are trying to correct the man by repeating him, a silly-sounding method of achieving something......

Old smooth bore projectiles would get really, really hot, because of the devils riding them.

That's why they invented spin, so the devils could not hang on.

Trying to summarize more than anything. No way all the factors are going to portrayed in an internet forum. Was hoping that someone would point out the obvious however- the equations involving rotation spin don't have enough information in them to conclude anything about bullets melting in flight. Also was hoping a lurking reading familiar with artillery would add a few comments on shell thickness vs. diameter etc. I'm sure the military has all kinds of "rules of thumb" on this stuff.

There was a thread a few weeks ago that went into detail about what causes a barrel to get hot.

I thought it was friction from the bullet going down the barrel, but some other readers gave good evidence that the barrel heat was from the burning powder.

However, does the friction of the bullet going through the barrel cause the bullet to heat up? I don't know, but would guess yes it does. The hot powder gasses acting on the base of the bullet would have some effect, but I don't know how much. For the short amount of time in the barrel, I doubt if the gasses would produce much heat the entire length of the bullet.

A far as which bullets would be most likely to melt, my only experience has been with a .220 Swift at about 4000 FPS, and with one particular bullet. No other brand of bullets left the puff of smokey looking tail as the bullet went down range.

So, I would conclude that for the core to melt, it would have to be with a fast bullet, in the range of 4000 FPS or so. Bearing surface would have some effect on how much and how quickly the bullet heated. The alloy of the core would have an affect on the melting of it. Then, like in my Swift, some bullets might melt and some might not.

Smoothness, or roughness of the bore might have some effect on the amount of friction and heat produced.

If you know the muzzle velocity and rate of twist, rpm is easy to figure out. Actually, it would be rate per minute, as the bullet is not in flight for a full minute. So is surface feet per minute easy to figure if you know the spin rate and the diameter of the bullet.

No, revolutions per minute is already a rate.

Maybe a really fast solid bullet (so it didn't explode on contact) could cook a rabbit when you shoot it.

Simply look at the heat required to melt a bullet and the amount of heat in a given amount of powder. Considering the energy available is inadequate to melt the bullet and then realize the total transfer of (heat) energy from the powder to bullet is extremely inefficient... There is absolutely no way the bullet can melt.
art

Reminds me of a thread a while back where some guys were saying that bullets actually melts holes in steel when shooting a steel plates.

Gotta love the seemingly "logical" explanations people contrive for things they can't get their heads around......and I think we all do one way or another. I still recall the first time I shot steel with a CF rifle (222 through a "tundra daisy"). (How does steel become liquid and resolidify so fast ? )

So are these fair to take away from this discussion?
* For a 1-12" twist the bullet will NEVER spin faster than the second foot of a 24" barrel?
* It spins at 100k's rpm (?) but will realistically never get close to spinning that many times?
* An average temperature of a given bullet is in the broad \ general range of 500 degrees F?
***Heat in the barrel comes mostly from the burnt gasses. To me this one seems to contradict other assumptions here about the minimal effects due to short duration - can anyone help me on this??? I am thinking perhaps friction plays more of a part than has been mentioned so far- just a thought. Guess comparing a moly bullet temp to a standard might be a good place to start. What else? Maybe how pressure plays into this perhaps???

Conclusion: bullet heat is not to worry about.