Multiple Bullets Stuck in Barrel (factory loads even!)

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The circumstances under which revolvers burst are therefore irrelevant to the topic.
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OIC, you thought the "revolvers burst" and that is the reason you applied the faulty deductive reasoning.

F. Guffey
 
The "experts" don't understand why barrels burst with obstructions. It is not the gas pressure, which barrels are designed to withstand, but the heat which results when a BULLET is stopped by an obstruction. The kinetic energy of the bullet is instantly converted to heat, and that heat is what softens the steel of the barrel and allows it to bulge or split. Since the gas alone does not have enough energy to do that, the barrel will not bulge from firing a POWDER ONLY cartridge.
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fguffey said:
Not the "experts" but barrels burst without obstructions. In the small circle of friends this is not a common event but when it happens everyone knows what caused it, then there was this other reloader/builder/shooter, he walked up the range a few yards to retrieve his barrel.

F. Guffey
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Ummm...

I don't understand who, exactly, these "experts" are who don't understand why barrels burst under certain conditions.

There is a field of engineering which concerns itself with exactly this kind of thing, and it's called "Fracture Mechanics".

Fracture Toughness is a measure of a material's ability to withstand stress without crack propagation (assuming a pre-existing flaw/crack). It is a distinct, measurable quantity which is affected by several factors, such as temperature, thermal stress, tensile stress, compressive stress, geometry, and the atomic crystaline structure of the material itself.

Bending stress is the amount of stress required to cause permanent plastic deformation of a metal (to cause a permanent bend).

When you speak of heat resulting from the Kinetic Energy of the bullet, the only way you get that heat from the KE is by converting some of it's velocity into heat through friction. When this happens, it heats the inner surface of the barrel where the bullet rubs along the grooves to a high temperature.

This creates a large thermal difference between the inner surface of the barrel along the grooves and the outer surface of the barrel. This large temperature difference causes what is known as "thermal stress".

Note that we're not talking about an absolute, uniform temperature of the barrel. A barrel which is the same temperature throughout the thickness of the steel effectively has no thermal stress, regardless of the temperature.

But the failure mode of concern here with all this applied stress is brittle fracture, not a ductile failure.

Brittle fracture is a sudden, catastrophic failure of a metal with a pre-existing flaw under a tensile stress with little or no plastic deformation. In otherwords, it "cracks" suddenly without any evidence of bending.

A rifle barrel isn't hard enough to fail by brittle fracture in the temperature ranges they are used in. They would have to be very VERY cold.

The failure mode of these rifle barrels is "ductile"...meaning it physically deforms by bending.

This is caused by excessive pressure stresses and NOT thermal stresses. (Remember, thermal stresses are due to temperature differences across the metal, not a uniform metal temperature.) Uneven external heating or cooling, however, can permanently warp a barrel, but that's for another discussion.

If you heat the entire rifle barrel up, then its ability to resist plastic deformation goes down. But you're talking about some pretty hefty 3-figure temperatures here.

ALL rifle and handgun barrels measurably expand and contract during use. You and I just can't see this with the naked eye.


The steel used in rifle barrels has a known fracture toughness. The stresses it is able to withstand for a given geometry can be calculated AND tested. The resulting finished produce is conservatively over-engineered such that the design pressure transients come nowhere near the actual stress limits of the barrel.


All things work together, but the ultimate bottom line is that if a rifle barrel becomes permanently deformed by a bulge, or ruptures, because of an obstructed barrel, it's because the pressure stresses that barrel was exposed to exceeded the bending stress limits of that rifle barrel and possibly the fracture toughness of that barrel.
 
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Zactly.

There is also the hydraulic forces of two solid and incompressible lead bullets running into each other with no where to go except outward.

Since lead cannot be compressed, something else has to give.

And that would be the barrel steel.

Hydronic force at a high enough pressure cannot be stopped until something gets out of the way to relieve the pressure.

rc
 
Nice.

A classic example of an overpressure transient exceeding the structural strength of the steel. I might save some of those pictures for a future training session on Fracture Mechanics. Entertaining pictures are ALWAYS a plus during training! Note the extensive plastic deformation evident in all the bent pieces. Classic ductile failure event due to overpressure.

:):)

Google the SS Schenectady to see the potential catastrophic effects of brittle fracture for a ship. And this ship was only a day old. She literally broke in half...tied up next to the pier.

http://en.wikipedia.org/wiki/SS_Schenectady
 
two cents, forgive, no one ask about the expansion of the forcing cone. But the inside diameter increased, the outside diameter also increased. When the barrel was removed the inside diameter of the hole in the frame also increased.

Then there were the gaps, no two were the same, I thought the bullets neatly stacked in the barrel was the least of his problems.

F. Guffey
 
fguffey said:
...I thought the bullets neatly stacked in the barrel was the least of his problems.

F. Guffey
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Indeed, you are correct. The question remains "Is the barrel damaged beyond use or repair?"

The problem with an overpressurization event is that there may not always be measurable evidence that the structure involved has been stressed excessively and would be, therefore, unsafe.

In Fracture Mechanics, the Fracture Troughness of a material always assumes the presence of a pre-existing crack. ALL metals have them...the question is where the crack is, how big it is, and how it's oriented. General assumptions are made with respect to the worse-case scenario. For example, the crack size is always assumed to be the largest size that can remain undetected by whatever inspection means is used, the crack location is always assumed to be in the region of highest stress, and the crack geometry is always assumed to be in the worst possible orientation relative to applied stresses.

Once an item is constructed, it is possible for a material to be exposed to excessive stresses (beyond the design tolerances) which may not cause permanent detectable damage...such as bends or bulges...but which may cause crack growth of the assumed pre-existing flaw beyond the assumptions made.

If this happens with a rifle barrel, then the barrel may not be able to safely operate within the design peak pressure limits it was originally built to.

Some structural materials, such as nuclear reactor pressure vessles and such, not only are designed with a lot of Fracture Mechanics studies done one them, their entire life cycle has a complete history of pressure, temperature, and power operation. If an overpressure event happens, such detailed records enable engineers to determine whether or not there was any effect on the assumed pre-existing flaws and therefore whether or not they need to change the operating envelope to allow continued safe operation.

However, you and I do not keep such detailed records on this kind of information which can be used to make that kind of decision. Rather, all we can go by is whether or not there was any permanent physical change to the firearm.


This is why I said in one of my earlier posts (#35) that I recommended retiring that barrel from service.
 
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wow you guys fight over everything . the man just needs help removing a blockage . i agree with WEG steel sectional rod close as possible to bore size and a hydrolic 20 ton press followed by a bore scope to see how it all turns out. we really dont care about welding drill bits its about removing a blockage . WEG old buddy you have the safest way short of sending it back to savage who will not warrentee the gun due to faulty ammo anyway.
28 years as a gunsmith if anyone is wondering ??
 
nulook45 said:
wow you guys fight over everything . the man just needs help removing a blockage . i agree with WEG steel sectional rod close as possible to bore size and a hydrolic 20 ton press followed by a bore scope to see how it all turns out. we really dont care about welding drill bits its about removing a blockage . WEG old buddy you have the safest way short of sending it back to savage who will not warrentee the gun due to faulty ammo anyway.
28 years as a gunsmith if anyone is wondering ??
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LOL!! Good post!:)
 
Either use the sectional steel rods and a hydraulic press, or put the barrel in a 5 gal bucket and add some mercury to the barrel. it will "melt" the lead and just pour out (if there are actually no jackets). If there are jackets, the mercury should melt the first lead slug, making it easy to pull the jacket, then repeat the process.
 
If barrels burst from the heat caused by the friction of the bullet rubbing on the barrel, every barrel would burst. Bursting is caused by pressure, but it is the heat dumped when the KE of a fast moving bullet is converted into heat by the sudden stop that softens the barrel steel and allows the pressure to bulge or burst the barrel. Even a cursory examination of a barrel burst due to an obstruction will show the effects of heat, not a bulge/burst due to pure pressure. That heat rises and dissipates so suddenly that usually the barrel bluing is not even damaged, as it would be in a slower heat buildup (from a torch, say).

Jim
 
OK my questioning mind wonders what happens to the piston of air that is trapped between the obsruction and the and the new bullet being fired .HMMMM it doesnt just disappear ?????
Chris
 
Air is very compressible. Scuba tanks with a static internal volume of about 0.6 cubic feet are pressurized to 3000 PSI to hold 80 cubic feet. Assuming it were all trapped between the projectiles, I don't see how the small amount of air in the barrel (maybe 1 cubic inch max in a large caliber revolver) could cause a bulge.
 
Still understanding air is compressible it has to go somewhere , it doesn't just dissappear .????
 
nulook45 said:
wow you guys fight over everything .
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Actually, this is pretty tame! It's really more of a discussion amongst those of us who disagree over some points.

:)


Jim K said:
If barrels burst from the heat caused by the friction of the bullet rubbing on the barrel, every barrel would burst. Bursting is caused by pressure, but it is the heat dumped when the KE of a fast moving bullet is converted into heat by the sudden stop that softens the barrel steel and allows the pressure to bulge or burst the barrel. Even a cursory examination of a barrel burst due to an obstruction will show the effects of heat, not a bulge/burst due to pure pressure. That heat rises and dissipates so suddenly that usually the barrel bluing is not even damaged, as it would be in a slower heat buildup (from a torch, say).

Jim
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Respectfully, I disagree.

Yes, KE is converted to heat when the bullet stops upon impact with the barrel obstruction.

However, that isn't the only, or even the most significant, effect. When the bullet is forced down the barrel towards the obstruction, there is a compressive pressure buildup due to mashing all that air between the bullet and the obstruction together.

When the bullet impacts the obstruction, there is also the pressure resulting from physical deformation of both the obstruction and the bullet.

Heat takes time to increase in a metal, as well as to dissipate. The higher the difference in temperature between the source and the object, the higher the heat transfer rate. However, in the split seconds that it takes for the barrel to rupture, there is no significant increase in the body of the barrel at the point of impact beyond some minimal surface temperatue increase inside the barrel. There simply isn't enough time for this. Therefore the structure of the metal beyond the surface of the inner bore is not radically affected by an increase in bulk temperature.


HOWEVER, a large temperature increase inside the barrel DOES cause a large thermal gradient through the barrel wall. Meaning an extremely high temperature inside the barrel and near ambient temperature on the outside.

The effect of this thermal gradient causes compressive stresses on the inside of the barrel and tensile stresses on the outside. (Tensile stress is stress that tends to pull a material apart...compressive is the opposite.)

Stresses, regardless of their source, are commulative...meaning they add up.
Total stress is thus the sum of the various compressive and tensile stresses at a given point in the metal, with compressive stresses countering the tensile stresses. If the resulting tensile stress applied exceeds the ability of the material to resist it, then the material will fail.


When a bullet hits a stationary obstruction in the barrel at high velocities, the back of the obstruction is forced towards the stationary front end of the obstruction, which has not yet begun to move at the instant of impact.

Likewise, the front of the moving bullet which strikes the obstruction starts to slow down...whereas the rear of the moving bullet has yet to slow at the instant of the impact.

The lead in the obstruction and the moving bullet, being incompressable and acting like a fluid at this point, will therefore expand outward and apply tremendous pressures to the sides of the bore at the point of impact. This sharp spike in pressure applies stresses far in excess of any instantaneus temperature effects.


While thermal stresses are, of course, present, the overriding stress being applied to the barrel is from overpressure...not temperature. The mechanical shock of two incompressable metals slamming into each other within a tightly confined steel barrel will cause a phenominal pressure transient through their deformation.

And the bulk temperature change in the metal does not significantly change during this event, and certainly not enough to soften the metal.

;)
 
I've personally seen multiple factory squibs obstruct a barrel. 3 consecutive rounds of Federal .38 Special SJHP, 125 grain. There were in the barrel of a Charter Arms Undercover.

20 years ago, I was shooting with my brother in law and his father. His father was shooting rapid fire strings. On a fresh reload, suddenly there were 3 very underwhelming pops. I don't even want to think of the odds that all 3 were squibs, in a row.

20 years ago, it wasn't my revolver, or my ammo, and yet I remember EXACTLY what ammunition and the full details of the event. (There was a later recall on that exact lot of ammunition.)

If it were my own firearm? Of course I would remember those details, as well. How can the OP not be certain of the ammunition? I think that we are only hearing part of the tale.
 
28 years as a gunsmith if anyone is wondering ??
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I wasn't, I was wondering why you did not take the time to explain how jammed up and bullet tight obstructions can be removed from a long barrel with a hydraulic press or an arbor press.



Then there is that mercury and its infinity, I suppose when finished with it a smith can just drive over to the north east corner of Oklahoma and dump it, that is an area that when it comes to hazardous material no one will notice additional contaminants.

F. Guffey
 
Sounds good, Chief. Now have you put a thermocouple on the barrel when you fired into a stuck bullet? Have you had the crystalline structure of the metal analyzed to determine what caused the stretching and tearing (like a warm chocolate bar) that is characteristic of barrels bulged or burst from firing into an obstruction. Those barrels don't fracture or break from pressure, they stretch like a balloon before bursting. Heat does that, a lot of heat. Like over 1000 degrees released so fast that the bluing isn't even disturbed.

Sorry, but compressed air is not going to burst a barrel; there is no way you can get enough pressure between the bullets. Also, there have been many experiments (one by me) with a hole drilled in the stuck bullet to release the air pressure. It made no difference; when the moving bullet stopped, the barrel bulged (that one didn't burst).

Jim
 
Of course I haven't. I don't destructively test rifle barrels. But I have studied Fracture Mechanics somewhat as an integral part of my nuclear engineering training over the past three decades. What causes structural failure, down to the atomic level of the material itself, is very important to me.

But just because I haven't tested rifle barrels to failure doesn't mean that I do not, or cannot, understand the mode of failure and what the most likely causes are. It's unfair to make that assumption.

If the bulk steel of the rifle barrel actually attained temperatures in excess of 1000 degrees Fahrenheit (as indicated by a minimum external temperature in excess of 1000 degrees), then the bluing WOULD show it and the color of the barrel would be a glowing, blood red color or brighter. And it would REMAIN that color until it cooled down on its way to ambient temperature, which would take time, just as it would if you heated any steel to that color. Unless the barrel is subsequently quenched, or otherwise rapidly cooled by some external means, the rate at which it cools would be the same as for any other steel of similar geometry heated to that temperature/color.

The instantaneous temperature of the internal surface of the bore would, indeed, rise. But it takes time for that temperature to radiate through the rest of the steel. Rifle barrels are routinely exposed to 3000-5000 degree temperatures down their bores through normal use. Yet you don't see the external tempertures reaching such high temperatures.

"High flame temperature propellants may produce combustion gases at temperatures
as high as 3700 K"

Source: http://precisionrifle.files.wordpre...tanding-and-predicting-gun-barrel-erosion.pdf

3,700 degrees Kelvin translates to 6,200 degrees Fahrenheit...and that's for a "high flame temperature" propellent, which I'm assuming represents the high end of the acheivable temperature range for propellents. The reason barrels don't suffer any radical temperature increases is because the normal exposure to these temparatures is limited to the time it takes for the bullet to exit and the high temperature gases to exhaust out the end of the barrel.

The only way you can increase the rate of heat transfer through a metal is to increase the temperature the barrel is exposed to. But even a radical increase in temperature caused by KE conversion will have it's effects dramatically outpaced by the sudden spike in incompressable fluid pressure in the instant that the bullet collides with the obstruction.

And that air compression? It, too, will cause a dramatic temperature increase, as well as a pressure increase. However, the pressure effects caused by rapid air compression are different than that of the impacting lead...because air is compressable and lead is not. If you read my earlier postings, you'll see that I never said that the pressure from the compressed air causes the bursting...I said that the pressure from the incompressable lead expanding outward does. Perhaps I was not clear enough when I first posted that, and I apologize for that.

Temperature effects aside, it is the expanding, incompressable lead at the instant of contact which causes the barrel to burst. There is insufficient time for the radiated temperature through the steel barrel to increase to the point where it would affect structural integrity. The pressure transfer through incompressable lead and incompressable steel is, for all intents and purposes, instantaneous. The heat transfer rate through the steel, however, is not instantaneous.
 
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Pineknot, I have a few of the very old bullet pullers, all one piece, most of the work for the old pullers was necessary because the bullet never left for what ever reason, caps, powder, no powder. And as you know, black powder works with lead that is dead soft.

F. Guffey
 
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