Rotational vs. Kinetic energy...

[BAGTIC]

The British tested every aspect of bullet heating while developing the .303 cartridge, they had to because both smokeless propellants and jacketed bullets were a new thing and early results were lousy.

They found that if a powder did not leave a smidgeon of carbon fouling, and the test batches of cordite burned extremely clean, then direct bullet jacket to bore steel contact overheated the jacket by friction alone, breaking the bond with the lead core and sometimes liquifying the outer surface of the lead core. Why didn't they have the same problem with black powder? When the first round is fired from a clean bore there is no 'carbon fouling' to lubricate the bore regardless of the powder being used. Powder fouling follows the projectile, it does not lead it.
They could see a halo of vaporized lead Lead vaporizes at 3189F degrees thrown from the base by centrifical force.At what point did they notice this 'halo' of vaporized lead? In the bore? If the hole had not been drilled in the bullet how would the lead vapor have escaped? Why does not modern ammunition experience this same melted core syndrome? If it exists we should be able to demonstrate it by firing at target close to the muzzle, before the 'melted cores' have a chance to solidify, and seing evidence of liquid splatter. Why don't we? The Hornady 7mm 120 gr SP chronographs at 3,281 fps from my 7x57 AI. It has never experienced 'melted core syndrome' It has not, yet, experienced bullets 'vaporizing' in flight. Why is that? It certainly operates at higher velocity, higher pressure, and higher temperatures than the .303.
A tiny hole drilled near the base allowed a plume of lead vapor to escape.

They tested to be sure it was mainly friction that overheated jackets by ramming bullets through the bore using a hydraulic ram then measuring heat of bullet and barrel. In 1891 where did they find a hydraulic ram able to force a bullet through a bore at 2,400 fps and 45,000 psi?

Several methods were tried to avoid partially liquifying the lead core. One was to insert a insulating layer between jacket and core, workable but costly.

They finally added mineral jelly to the cordite formula, the mineral jelly (only rifle and artillery cordite used mineral jelly, pitol cordite and blank cartridge cordite do not) left a microscopic carbon layer to prevent direct contact. The mineral jelly was added to reduce the combustion temperature of the early cordite temperatures which experienced severe throat/bore erosion. This applied to artillery firing steel projectiles which certainly were not being softened by the temperatures.Still the first shot from a clean dry barrel usually went wild. Of course. Accuracy is about repeatability and consistency. It requires consistent bullet weight, charge weight, etc. When one introduces two different bore conditions (clean/dirty) one introduces variability. If bore were cleaned between every shot such as many old time lead bullet target shooters did, that variability would have been removed. It would however have been inconvenient in combat. I am sure that if one excludes the first shot from the clean barrel the remainder would have exhibited much more uniform performance.
They then increased jacket thickness and added alloying metals to the lead core material.
Together these steps did the trick.

How much the heating of modern bullet designs comes from friction is hard to say, but I would expect that its most.

When the .220 Swift was first pushed past 4,000 FPS bullets sometimes flew apart within feet of the muzzle, a white trail of vaporized lead [3180 f degrees] was shown by high speed photography.
The bullet flew apart due to centrifical force, but could not have done so if not heated to the melting point of lead by friction. If it was due to frictional heating can we assume that it happened to every shot fired for surely that all experience the same friction? I personally have had two bullets diintegrate in the air at close[< 50 yrds] range. This out of many thousandsfired using the same gun and load over the past 50+ years. Friction sure is fickle isn't it?

The hotter the propellent the more heat the bullet is already exposed to by the time its velocity reaches the point where friction heats it to its maximum temperature before leaving the bore. Only at the very base
Air resistence may add heat to the nose but passage of air would also carry heat away from the body. So will radiation.
Another minor factor might be heat of compression due to bump up and engraving forces at the begining of its trip.

If there significant blowby this can also overheat the already hot jacket, this was the major cause of shed jackets stuck in the bore. The higher the propellent temperature the more likely that blowby would damage the jacket.
The over the charge card wad of the .303 reduced blowby,Ley's see. The brass jacket could not prevent blowby but the little paper wad could. Does that seem reasonable? without the card the thoat would be destroyed in 1/6th the number of rounds fired.

From WIKI, "The Lee-Metford started to be phased out in 1895 in favor of the Lee-Enfield, which was a virtually identical design but adapted for the use of smokeless powder. The Metford pattern of rifling was shallow and subject to rapid wear when ammunition loaded with cordite was used, with barrels becoming unusable after less than 5,000 rounds. Changes included a new, deeper rifling pattern (designated Enfield pattern) and sights adjusted for the flatter trajectory enabled by the smokeless propellant." No mention of the 'marvelous new anti-melt bullet design.
Where were the British getting all of these marvelous technological devices in 1891?

[leftiye]

I wish you'd quit doing that, I can't read it.

[leftiye]

So, this heat idea may actually be having an effect? The reference to a modicum of carbon used to reduce friction would say that actual lubricants would cause much more heat reduction. But it appears that plenty of heat is available. Wow, melt lead cores inside jackets!

[BAGTIC]

If you are color blind I could try a different color.

Website boards have a lot in common with the rest of life in that much of the information on them is worth only what one pays for it. Much is opinion, speculation, conjecture none of which constitutes evidence. GIGO

I offer some evidence.

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


The boiling point of lead is 1750 C. The melting point is 328 C. All are above the measured temperatures. Aerodynamic heating of the tip was only 170 C. Note that the hot spots were in the grooves cut by the riflings lands. The spaces between those grooves where the bullet rode over the grooves was much cooler and did not glow as much as the aerodynamically heated tip.

[Nrut]

Blue would work for me...

[DrB]

Nice find, bagtic. There are several factors which affect frictional heating, though. I would really like to read multigunners sources for myself to get a better idea as to conditions and observations.

I have heard anecdotes of very high velocity >4000 fps 22 cal rounds leaving silver "rays" of lead around a target hole that were assumed to correspond to cracks in the jacket from rifling scoring. Previously I had assumed the core was spun past ultimate stress and was leaking out from centripetal force, but after calculating the stress I don't believe this is possible for the scenario.

I haven't observed the leaking lead, but if it is happening then it must be something besides just centripetal acceleration. It can't be aerodynamic, and I don't believe it can be heat transfer from the combustion gases. That leaves rifling friction? Anything else?

Best regards,
DrB

[leftiye]

So, if we go back to cast boolits, heating until softened may be possible? You only need for it to occur in the grooves made by the rifling, and then only on the edge that bears for trouble to ensue. Heating would also grossly exacerbate slumping.

Too old to be color blind and to not have it shown up at the optometrist's office. Jest a nasty color.

Had to add - Mighty nice of you to offer evidence that supports the side of the issue that you are disparaging.

[Multigunner]

From WIKI, "The Lee-Metford started to be phased out in 1895 in favor of the Lee-Enfield, which was a virtually identical design but adapted for the use of smokeless powder. The Metford pattern of rifling was shallow and subject to rapid wear when ammunition loaded with cordite was used, with barrels becoming unusable after less than 5,000 rounds. Changes included a new, deeper rifling pattern (designated Enfield pattern) and sights adjusted for the flatter trajectory enabled by the smokeless propellant." No mention of the 'marvelous new anti-melt bullet design.
Where were the British getting all of these marvelous technological devices in 1891?

Try T F Freemantle (Lord Cottesloe) "The Book of the Rifle"
From page 90

One difficulty connected with the bullet gave some little trouble at first. The heat set up by the friction of the bullet on the bore is very considerable. It was found with the experimental ammunition first made for the .303 that the first shot fired from a clean barrel was never seen or heard of again, while, when once the barrel had been fouled, the rifle shot satisfactorily. The only reason was that the friction of the bullet in being passed up the barrel developed heat enough to melt that part' of the leaden core which lay next to it. Apparently the deposit from a shot previously fired was sufficient to reduce this heating effect. The difficulty was so great that it had to be got over by thickening the metal envelope of the bullet. It could equally have been overcome, as Sir Henry Halford pointed out in a lecture delivered at Aldershot at the time, by inserting a minute layer of some non-conducting material between the leaden core and the metal thimble. Some years ago the writer was trying a series of experiments with various loads of different smokeless powders, and a bullet of normal make which gave no trouble. In testing one particular powder at the ballistic pendulum the shooting was found to be extremely wild. On firing a series of shots through a cardboard target at a distance of only 4 or 5 yards, the reason became evident. Most of the shot holes were seen to be surrounded by one or more little black cloudy marks, sometimes showing a spiral inclination, which proved clearly enough that a spattering of very fine particles of melted lead was escaping from the base of the bullet as it flew. Why the conditions of friction with the deposit of this powder were so different from those of all other powders used with the same bullet, it would be very hard to say. Mr. Metford, in investigating the vagaries of the first shot, had been able to see the bullet in the air surrounded, as it flew, by a little cloud of melted lead consisting of particles so fine that on recovering the bullet, and weighing it, it was found to have lost only one or two grains in weight during a flight of several yards through the air.

Another adverse effect of Cordite without mineral jelly was the tendency of jacket material to bond to bore surfaces so thickly that accuracy went south within 400 rounds. The thick metal fouling was so difficult to remove that barrels were often ruined in the cleaning process.
Carbon fouling then proved to be beneficial. Of course you can have too much of a good thing.

Freemantle gives only a small part of the story. There are other contemporay sources that give a better picture of the order of events.

Wikipedia doesn't really have much useful information on the development of the .303 cartridge, or its propellents and bullets.

PS
You'd be suprised just how high the engineering arts advanced during the last years of the 19th century.

[303Guy]

I wish you'd quit doing that, I can't read it.

It's not alway apparent. I've just just installed a new operating system (old one got hijacked and destroyed - and the swines phoned me and offered to go into my 'puter to fix the problems they'd caused in the first place! What? They think I got money in my bank account they can steal! And they would have too!) and the screen colors make it very hard to read the green.

PS
You'd be surprised just how high the engineering arts advanced during the last years of the 19th century.

It is very surprising indeed!

[Multigunner]

It is very surprising indeed!

The first use of "Spark Photography" (invented in 1850) to photograph the passage of a bullet through the air was done in 1886.

PS
Two things about paper.
Paper or cardboard wadding doesn't burn up so easily because propellents generally only create as much oxygen as they use up in combustion. No matter how hot it gets, where theres no oxygen theres no oxydation. The same principle that allows the lightbulb filament to last so long at incandescent temperatures in its vacuum sealed environment.

Paper is also a very effective insulator, copper and other bullet jacket materials conduct heat with great efficiency.

[303Guy]

The first use of "Spark Photography" (invented in 1850) to photograph the passage of a bullet through the air was done in 1886.

Wow!

I'd suggest that there simply isn't enough time for heat to be transfered into paper and not much to transfer into copper. Friction will heat a copper jacket pretty quickly though (on the contact surface). Yet a hot flame under high pressure will erode lead violently in the same time. Or does it at very high velocity? Surface friction heating and melting might become more dominant at higher velocity.

[HORNET]

Charles Newton had problems with bullets coming apart in flight with the .30 Newton and attributed it to melting (or at least softening of the outer portions) of the core due to friction. He had the makers insert a paper wrapping on the cores and the problem went away. I don't know if that was due to the insulation effect or because it gave a "yield zone" for the jacket to deflect into and reduce stress riser formation which would effectively give a stronger jacket on barrel exit. A comparison of standard rifling versus the 5-R type might also be interesting, maybe in a .22-250 where I have had varmint bullets go "blue cloud" in flight.
Strange things happen to material properties under extremely short term high intensity transients of heat and pressure. There is little published data on this that I've been able to find and I suspect that variations in exact alloy composition may have a significant effect on the properties (strain rate sensitivity, heat transfer rate, etc).

[BAGTIC]

Had to add - Mighty nice of you to offer evidence that supports the side of the issue that you are disparaging.

Why not? In the search for truth there is no room for egos. The truth must out.

When using long ago references it is important to remember that those conclusions are just that, conclusions, and they they were as subject to error as we are today. The difference is that we have had more time to check, recheck and compare. Also we have much better technology.

Many great scientific discoveries and theories have been based on original error. Example, Gallileo's cannonbal experiment whereby he deduced that rate of fall is the same for cannonballs of all sizes. In a vacuum, yes, but in northern Italy , no. It was the result of the fact that with the technology available to him at the time he was unable to accurately measure the difference caused by aerodynamic drag. Remember the great Isaac Newton predicted the world will end next year and several Nobel Prizes have been found invalid because later research proved the to be erroneous..

[leftiye]

Surface friction heating and melting might become more dominant at higher velocity.

Trying not to be a yerk (yeah, it's hard), - but that's the whole point. Faster = hotter. Threshold anybody?

[Multigunner]

When theres little or no effective cooling process heat will continue to build up from any sources that create and transfer it.
When a bore has eroded sections, gas blowby adds to the heat of friction. A bullet otherwise resistent to effects of friction heating can be pushed past the tipping point by blowby.
When the Springfield 1903 .30 caliber loaded with high nitroglycerine content double base powder was in use, eroded sections allowed blowby that overheated the bullet jacket causing blow throgh of the lead core and leaving jackets stuck in the bore.
A report to the Chief of Ordnance outlined the cause and cure. Bullet manufacturing processes and thicker jackets solved the problem. Use of a much lower temperature single base pyro-cellulose powder for the 1906 .30 cartridge greatly reduced erosion.
Where stuck jacket removal tools had been part of evey Springfield cleaning kit, now only a few were issued per company for use by officers and non coms trained to use these properly to avoid bore damage.

Black Powder cartridges used bullets with lube grooves and/or surface applications of thick lubricants to reduce friction, otherwise few bullets could leave the bore intact.
Bullet seize up and blow through could still be a problem with too soft bullets and roughened bores.
Surface seasoning of the bore lessened friction by trapping microscopic globules of lubes that acted like miniature ball bearings under these pressures. The microscopic pits , visible only as a darkened surface held just enough lube to prevent or lessen metal to metal contact.
Brightly polished bores caused more friction not less as we would expect. Same principle as the crosshatch honing of automobile engine cylinders to hold lube during the firing stroke.
When in balance the rings don't actually touch the cylinder walls. A ultra thin barrier of oil seals in the high pressure combustion gases rather than metal to metal contact.

A proper BP/lead boolit bore should be even but not slick other than the slick coating of lubes.
Slick polished or burnished steel won't hold enough lube.

Paper patching of bullets served several purposes at once. Under pressure paper becomes stronger, and quickly reaches the point of relative incompressibility. Lead remains ductile far longer than paper.
Greased leather and later cloth patches served the same purpose for the round ball muzzle loaders.
Paper patching allowed duplex bullets with softer lead body and hardened lead nose sections to be used with a false muzzle for the most powerful of the muzzle loading thousand yard match rifles.
The soft body upset to push the paper jacket deep into the grooves, the paper insulated the soft lead from friction heating, the hard nose section withstood acceleration and air resistence which would otherwise deform a soft bullet nose at these power levels.
Still BP cartridges had velocity limitations.
The few hundred extra FPS of early smokeless powder cartridges pushed the older style bullets past the tipping point of consistent performance.

As for powder grain peening of bullet bases, this is a recognised factor in forensics. I've seen the effect on open base FMJ pistol bullets I salvaged from a clay bank after a hard rain. The 9mm seems to demonstrate this more clearly than lower pressure rounds, or higher pressure rounds which have tougher core alloys.
Lead is deposited in the bore in microscopic amounts every time an open base bullet is fired. The following shots carry away most of the lead from the previous shot.
The microscopic lead contamination of the bullet jacket is then scrapped away when the bullet penetrates a hard object, like wall board or doors.
A chemical that detects lead can be used to identify bullet holes that otherwise might be overlooked, or tell the difference between old nail holes and bulletholes.

PS
Another historical tidbit.
The Thermocouple was invented in 1821.

PPS

The temperature required to volatilize/boil lead is 1,740 C or 3,164 F

Vaporize is not the same as "volatilize".
Water can be vaporized by merely squirting it from a spray bottle at room temperature, it doesn't have to reach the boiling point, much less the ultra high temperatures that can cause the oxygen/hydrogen bond to break resulting in water burning as two gases.
Lead does not have to volitalize or oxydise in order to form a vapor, "vapor" is not the same as a gaseous product of combustion.
The term "vaporize" is an imprecise term, subject to mis interpretation.

Its greatly dependent on pressure as well as temperatures.

A vapor (American spelling) or vapour (see spelling differences) is a substance in the gas phase at a temperature lower than its critical point.[1] This means that the vapor can be condensed to a liquid or to a solid by increasing its pressure without reducing the temperature.

For example, water has a critical temperature of 374 °C (647 K), which is the highest temperature at which liquid water can exist. In the atmosphere at ordinary temperatures, therefore, gaseous water (known as water vapor) will condense to liquid if its partial pressure is increased sufficiently.

A vapor may co-exist with a liquid (or solid). When this is true, the two phases will be in equilibrium, and the gas pressure will equal the equilibrium vapor pressure of the liquid (or solid).[

And the differences in pressures are very great during the stages between ignition and the bullet leaving the muzzle.

[303Guy]

Thanks for all the interesting bits of information, Multigunner. (Thermocouples are that old?!!)

The microscopic pits , visible only as a darkened surface held just enough lube to prevent or lessen metal to metal contact.
Brightly polished bores caused more friction not less as we would expect. Same principle as the crosshatch honing of automobile engine cylinders to hold lube during the firing stroke.

These 'microscopic' pits seem to hold lube very well. This bore gets no copper fouling at all! (It just doesn't seem to like plain cast or paper patched boolits). The j-words do get a dose of 'waxy-lube' before seating. The rifle is accurate too.

[Multigunner]

Thanks for all the interesting bits of information, Multigunner. (Thermocouples are that old?!!)





These 'microscopic' pits seem to hold lube very well. This bore gets no copper fouling at all! (It just doesn't seem to like plain cast or paper patched boolits). The j-words do get a dose of 'waxy-lube' before seating. The rifle is accurate too.

From what I can see that bore is a bit past what I'd consider properly seasoned.
The surface isn't exactly rough in the same way as it would be if pitting had sharpe edges , its more rippled.
Some custom barrel makers have developed their own method of surface finishing of the bore to reduce friction on bullet jackets, the effect is much the same as the bore section you show here.
The problem of lubes with J-word bullets comes from the much higher pressures and velocity of most centerfire jacketed bullet loads. Lubes loose lubricity under great pressures, some more quickly than others.
There was a .30-40 Krag match grade bullet that had both jacket and lube grooves. They found this bullet worked very well, but that it worked better if no lube was used. The groove without lube reduced surface area in contact with the bore so friction was lessened.
The sealant groove near the base of the early milspec .303 FMJ bullets, the point where the stake crimp is applied, held a "beeswax" sealant/lube that would have had very little actual lubrication properties at those temperatures and pressures, but may have reduced friction by reducing surface contact. It also served to reduce possibility of core blow through by gripping the core firmly near the base.
Some solid bronze alloy bullets have grooves that look like lube grooves of lead bullets but these are there to reduce surface contact friction to reduce pressures and reduce bullet heating as well. No core to blow through, but less heat would mean reduced metal fouling and other beneficial effects.

Most metal objects begin to lose structural strength at relatively low levels of heating. Titanium's major benefit in use for supersonic aircraft is that it does not lose structural strength at high temperatures.

The forces at work on a bullet are awesome, G-forces of acceleration are terrific, pressures and shock of acceleration compress and deform metals producing heat on their own besides the heat transfered by propellent gases and friction.


PS
In case I didn't get the point across about Vaporization. If water had to reach the boiling point to become a vapor there would be no moisture in the air and no clouds.

[303Guy]

That bore had been fire-lapped before I cut the tip off. It is a little past what would be considered 'textured'. The lube I use is applied by dipping the bullet base into molten 'waxy-lube' where a cup of lube remains on the base and chamfer when seated. The purpose is actually to deposit a protective coating inside the 'suppressor-break'.

[BAGTIC]

Much of the barrel fouling that was common in the early days, before Cordite had the vaseline added, was due to the use of Cupro-nickel jackets and not connected to cordite use as it also affected rounds loaded with single-based powders.