Projectile/Bullet Tempreture at what FPS?

[F.A.C.T.S.]

Speed causes friction, friction causes heat, at what speed (FPS) does the lead tip melt off the projectile/bullet. Is their a calculation to determine the tip temperature of a speeding bullet/projectile?

 

[yugorpk]

The friction necessary to melt the lead tip of a bullet is going to take place at a point considerably faster than the speed of a bullet. Maybe if you fired it from a low satellite and it was going through reentry.

 

[rcmodel]

This is not correct.

It is quite common to have lightly jacketed small bore varmint bullets turn into a puff of blue smoke 50' in front of the muzzle in rifles capable of 3,600 - 4,000 FPS.

That includes the 22-250, .220 Swift, and several of the centerfire .17 & .20 calibers.

Whether or not it is the bullet disintegrating due to the high RPM from the rifling spin, or if the bullets begin to melt from air friction, I cannot say.

However, Hornady just discovered the plastic tips on their long range match bullets were melting off at extended range, ruining the Ballistic Cofficient and long range accuracy.

They just announced the new ELD-X plastic bullet tip that will withstand air friction melting at all ranges.

rc

 

[JohnKSa]

Shooting USA did a segment awhile back about some research that Hornady did on why they weren't seeing the predicted ballistic coefficient they expected from some of their polymer-tipped ammo. Turns out the bullet was getting hot enough from air-friction that it deformed the polymer tip. Unfortunately I don't remember the temperatures involved.

Hah! rc beat me to it by seconds.

Whether or not it is the bullet disintegrating due to the high RPM from the rifling spin...

That's the explanation I had always heard.

 

[Bobson]

The melting point of lead is 621.5 degrees F. I don't know how much heat is generated by a small, aerodynamic projectile flying through the air at 2500 FPS, but I'm going to go out on a limb and guess that it doesn't heat up much beyond a few degrees. If you find out, let us know.

My guess, along the lines of guessing the number of jelly beans in a 50 gallon fishtank, is the bullet would need to approach 35k FPS. I think the wind itself would be peeling lead from the tip long before it could begin to melt from generated heat.

 

[rcmodel]

You have to remember the bullet gets very hot due to friction just in the short trip out the barrel.

Whether the lead core reached melting temp or not?
Probably not or the bullet would turn to vapor instantly.

But it's long been a known fact that the very high velocity varmint bullets turn to a blue grey puff of smoke when the jacket fails to keep the lead core contained.

That tells me the lead melted when subjected to air friction at 4,000 FPS.



rc

 

[denton]

M855 bullets exit the muzzle of am M16 very close to the melting point of lead.

 

[JohnKSa]

Some interesting information here.

http://www.thehighroad.org/archive/index.php/t-434865.html

http://www.handloads.com/forum/showthread.asp?topic=5&thread=252

 

[rcmodel]

This is an interesting study.

Note the high temperature generated by the friction from the rifling.

http://www.advancedimagingpro.com/print/Advanced-Imaging-Magazine/Infrared-Camera-Measures-Bullet-Heating/1$180

(Well darn! I can't get the link to work.

http://www.advancedimagingpro.com/print/Advanced-Imaging-Magazine/Infrared-Camera-Measures-Bullet-Heating/1$180


rc

 

[olafhardtB]

That powder burning behind the bullet is pretty hot.

 

[rcmodel]

Not near as hot as the copper jacket friction screaming down the rifled barrel.

rc

 

[Bobson]

Double post.

 

[Bobson]

And that powder behind the bullet is only effecting the bullet (transferring heat) for thousandths of a second. Even if it's 1000 degrees (and it's nowhere near that hot, or brass cases would have a life of one shot), the bullet isn't going to be effected by it much at all. Especially not the nose of the bullet, which is what we're talking about here.

As far as heat transfer from contact with the rifling, remember we're talking about the small lead tip exposed at the nose of a bullet, wrapped in copper or alloy of some sort. The lead isn't contacting the rifle's barrel; it's insulated and only gaining heat by contact with another heated metal. Like putting a room temp frying pan on a red hot oven burner, sure it heats up quickly, but it can be minutes before the temps are the same. And just as with the heat from the powder, the case of the bullet is only exposed to the barrel for fractions of a second, at which point it hits open air and begins cooling at an almost incomprehensible rate.

But it's long been a known fact that the very high velocity varmint bullets turn to a blue grey puff of smoke when the jacket fails to keep the lead core contained.

That tells me the lead melted when subjected to air friction at 4,000 FPS.

No disrespect intended, but your interpretation of a blue grey puff of smoke being evidence that the lead has liquefied just doesn't hold up. What you're describing is what we would expect to see if a bullet disintegrated due to incredible friction, more like what we see when a bullet impacts a steel ringer and "splashes." Furthermore, we already know why this happens - excessive velocity peels the jacket from the core, at which point the bullet does in fact come apart and disintegrate. Liquification/melting has nothing to do with it.

M855 bullets exit the muzzle of am M16 very close to the melting point of lead.

According to who or what?

 

[lysanderxiii]

And that powder behind the bullet is only effecting the bullet (transferring heat) for thousandths of a second. Even if it's 1000 degrees (and it's nowhere near that hot, or brass cases would have a life of one shot), the bullet isn't going to be effected by it much at all. Especially not the nose of the bullet, which is what we're talking about here.

As far as heat transfer from contact with the rifling, remember we're talking about the small lead tip exposed at the nose of a bullet, wrapped in copper or alloy of some sort. The lead isn't contacting the rifle's barrel; it's insulated and only gaining heat by contact with another heated metal. Like putting a room temp frying pan on a red hot oven burner, sure it heats up quickly, but it can be minutes before the temps are the same. And just as with the heat from the powder, the case of the bullet is only exposed to the barrel for fractions of a second, at which point it hits open air and begins cooling at an almost incomprehensible rate.


No disrespect intended, but your interpretation of a blue grey puff of smoke being evidence that the lead has liquefied just doesn't hold up. What you're describing is what we would expect to see if a bullet disintegrated due to incredible friction, more like what we see when a bullet impacts a steel ringer and "splashes." Furthermore, we already know why this happens - excessive velocity peels the jacket from the core, at which point the bullet does in fact come apart and disintegrate. Liquification/melting has nothing to do with it.

According to who or what?

[red] The flame temperature of single based propellant is in the 2700° to 3000° range. The gas temperature at about 10 inches from the chamber is still around 1500° to 2000°. Double and triple base propellants get hotter, into the 3500° range.

Yes, the heat transfer is far to slow for the 3000° gas to melt the lead in a bullet. (Otherwise lead bullets would never work.) The same reasoning is why brass cases last.

At Mach 3 at sea level (3375 fps) on a 'standard day' the stagnation temperature is 540° F. The stagnation temperature is the temperature of the air hitting the very tip of the projectile nose. But, that does not mean the nose gets that hot as there is also heat transfer from the nose the projectile to the interior, and subsequent heat loss back out to the atmosphere.

 

[lysanderxiii]

That powder burning behind the bullet is pretty hot.

Not near as hot as the copper jacket friction screaming down the rifled barrel.

rc

The friction temperature in the link provided was around 600° F, the reflected temperature of the gas was above 900° F…

 

[Sunray]

Lead melts at 327.5 °C (621.5 °F). No bullet at any speed(isn't speed that causes friction either.) will ever get that hot. A spent bullet isn't hot enough to char wood or the paint on it. It is hot enough to burn your hide.
There is no formula. Too many variables.

 

[Bobson]

[red] The flame temperature of single based propellant is in the 2700° to 3000° range. The gas temperature at about 10 inches from the chamber is still around 1500° to 2000°. Double and triple base propellants get hotter, into the 3500° range.

Very interesting. Thanks for the correction.

I didn't think it could possibly be so hot... There are many different compositions of brass alloys, with varying melting points, but all of them that I've seen have MPs below 2000 degrees F. If the ignited propellant is pushing 3500 degrees F in some cases, how does the brass (which is in more or less direct contact) survive?

 

[Jim Watson]

Mr Newton put a wrap of paper between the lead core and copper alloy jacket of his high velocity bullets as insulation from barrel heat. He also put a steel pin down from the soft point into the body of the core to protect the nose from deformation.

We used to read of "comets" of melted lead on targets shot with varmint bullets.

I read of one guy shooting a load marginally fast for the bullet. It did fine in a lapped match barrel but would blow up the bullets if shot from a mass produced barrel that had not been lapped.

 

[Tirod]

It's not hot enough to melt gilding or lead as the bullet gets pushed down the barrel. Friction of the bullet engraved in the rifling is part spin, and partly resolved by abrasion. The material in contact with the rifling is simply being torn off as if a finely honed file was working on it.

Push a bullet so fast that it actually melts as it passes down the barrel and gas would bypass it on the weakest side, causing horrible inaccuracy as the misshapen lump exits the muzzle with high pressure jets upsetting it.

Yes, a maker did change the formula for their polymer tips to resist heat, because they found that any polymer tip would melt. Which is rather a forgone conclusion as that is one quality of the material and why its chosen - to be formed when hot to it's shape.

What Hornady found was that bullets over Cd 550 G1 at high velocities when shot over 400m were melting their tips. It took having a very efficient profile to keep the bullet at a higher velocity long enough to actually melt them. The average load doesn't do that. And because of that, not everybody is jumping on the high heat resistant polymer bandwagon just yet. http://www.thefirearmblog.com/blog/2015/10/29/hornadys-big-announcement-eld-x-heat-shield-tip/

The bullets were still intact at the point of impact - the gilding jacket wasn't compromised, just the tip where most of the extreme friction takes place. With that in mind, the subject becomes much more academic for most of us - it only affect extreme load shooters at long range precision targets. The rest of us - hunters, LEO/Mil, self defense - will never see it at the short ranges we engage at. It's a prairie dog thing.

 

[jmorris]

I have seen bullets disintegrate due to centrifugal force like RC was talking about in #3. Same load one out of a 1:14 twist barrel is fine but it will come apart out of a 1:7, they were old Speer thin JHP bullets. That is not a heat issue though.

Hornady recently found that their plastic tips had been melting and changing the shape of the bullet resulting in loss of BC.

In this video,https://www.youtube.com/watch?v=EnpwnYc0Sh8

Starting around 5:37 they show a simulation of some bullet fired and tip temperature.

At 2875 fps they show a temp of 792 degrees (I am going to assume F)
@ 2500 fps, 613 deg
@ 2262 fps, 519 deg

It might be worth noting that they don't offer a .224 bullet with the heat shield tip and it is not uncommon for them to operate well over 3000 fps. Also 792 F will melt the lead out of any bullet, if it gets to that temp but they obviously don't reach that internal temp to they would "splat" vs expand. A faster bullet will also get to the target faster than one moving slower, exposing itself to the heat for less time.

Other factors are also in play as well. Plastic is an insulator where lead is a conductor. So, a heated lead bullet would be more likely to conduct the heat from the tip to the rest of the lead vs holding it in the tip.

To illustrate this you can get lead, copper, steel and plastic rods, all the same diameter /length and hold each one (at the same point) above a flame and see what one you can hold the longest. If you have graphite it is neat to play with as well, one end can be glowing after enough time, and you can still hold the other end.

Also you can expose a lead bullet to a temperature of thousands of degrees, if the duration is short enough, you will see no damage. If you have some bullets and a torch you can see this for yourself; however, if you expose one to say 625 F long enough it will melt but no bullet would be in flight that long. That said, as above it was long enough to melt the non conductive tip that Hornady uses on other bullets (fired in some rifles at extended distances) to melt the plastic they use in them.

One other factor could be heat dissipation, for all intents and purposes a bullet flight is fairly instant, would take some testing how much heat the rest of a lead bullet could transfer from the tip down before melting.

Maybe some food for thought...

I would also be quite interested in being paid to find out the answers, an interesting subject indeed.

 

[J-Bar]

If the burning powder gases are not capable of melting lead, how does one explain lead accumulation in a barrel when using cast (non-jacketed) lead bullets in a high velocity firearm?

I thought it was explained by using a lead alloy that is too hard to allow the bullet to "bump up" to groove diameter, which would allow hot gases to leak forward around the base of the bullet, resulting in lead deposits in the barrel. If hot gases are not capable of damaging cast lead bullets, why use gas checks?

 

[benEzra]

But it's long been a known fact that the very high velocity varmint bullets turn to a blue grey puff of smoke when the jacket fails to keep the lead core contained.

That tells me the lead melted when subjected to air friction at 4,000 FPS.

Lead doesn't have to be a liquid to fragment. It will also fragment if you spin a piece of it at 350,000+ rpm. Once centrifugal force exceeds the tensile strength of the lead (which AFAIK is less than the plastic in milk jugs), it comes apart. Remember, you're talking about a metal so soft that it can be scratched with a fingernail.

 

[gearhead]

Lead core bullets lose accuracy when a firearm is shot hard enough to get the barrel really hot too, if you let a round sit in a chamber that's hot enough to soften the lead the jacket will spin up but the lead doesn't spin up as fast. That causes the bullet to jump when it leaves the muzzle.

 

[243winxb]

Bullets not reaching the target or nose melting.

Not Berger Photos. A rough throat/bore in long barrels produce heat, causing bullets to fail. To much RPM adds to it. Berger bullet failure test (2008). Infared images- core melting. http://benchrest.com/showthread.php?49336-Berger-bullet-failure-test And yes, i have had a spitzer nose melt out of a 243win. because of barrel conditions. Lead smears on the target, like in the photo. (not mine) Berger has made changes to there bullets, to correct problems that were posted in the 2008 link above.

 

[benEzra]

243winxb, those are great pics. I've never seen that phenomenon on the target before. I learned a lot from that link.