Copper or Aluminum

[Larry Gibson]

Then why doesn't the paper patch on paper patched bullets just burn up? You know the highest percentage of heat on the bullet is from friction. Sometime look up friction welding on the internet. Want more proof? Have a contest to see who can bolt, pump, lever a fired case out of a rifle the fastest. I bet that case isn't even luke warm. Next take any semi auto and fire the same load and try picking the empty up...even 22 rimfires are real hot. Ever had one go down your shirt? Need more proof....make bow fire starter. There's no flame heat there, it's all 100 percent friction heat.

The bullet along with it check are only in the barrel in the nano seconds. This was talked about when some people say firing a harden lead alloy bullet totally anneals it. Not enough time and there is no evidence of the recovered bullet being as soft as if it were annealed when it hits the target, that is in the dirt, wood, etc.

It's not really the friction causing the most heat on the GC. It is the pressure. When a metal or anything else is compressed, it creates heat. The greater the compression the greater the heat produced. The pressure creates compression of the GC and the shank. Also, the higher the psi of the load the more heat is generated by the burning gas. Thus at 50,000+ psi it appears there is sufficient pressure on the GC to create sufficient heat. The paper is an excellent insulator and does not convey heat well and probably its compression does not create the same heat. Additionally, since PP'd bullets are not shot at 50,000+ psi successfully we don't really know if the paper is or would be burnt or not.

[TD1886]

It's not really the friction causing the most heat on the GC. It is the pressure. When a metal or anything else is compressed, it creates heat. The greater the compression the greater the heat produced. The pressure creates compression of the GC and the shank. Also, the higher the psi of the load the more heat is generated by the burning gas. Thus at 50,000+ psi it appears there is sufficient pressure on the GC to create sufficient heat. The paper is an excellent insulator and does not convey heat well and probably its compression does not create the same heat. Additionally, since PP'd bullets are not shot at 50,000+ psi successfully we don't really know if the paper is or would be burnt or not.

Yes pressure creates heat. I don't agree with on your assumption. My assumption is it's friction. There is only one way to prove it that I know of and that would be to fire the bullet in an air rifle that would put that much pressure behind the bullet and of course the friction would be present.

Apparently you have forgotten the NRA's paper patch test of the 300 Winchester Magnum using 150, 169, and 180 paper patched bullet and accuracy was 1.47 inches in a 25 mph wind. Actually groups varied as they changed alloy. They did rather good and that shows that paper patch did hold up to the powder heat.

Back to the heat from the powder burn why doesn't Kapok catch fire and also many of us shooter find Dacron tuffs in front of our shooting benches. I don't know about other, but the loads I used those materials in wasn't just lower velocity loads.

[gloob]

^Please be careful, there, Larry. Boyle's Law applies to gases, only. Liquids and solids are incompressible.

The only heat to the check that would be indirectly caused by pressure would be due to mechanical deformation/flow of the copper as the pressure formed it to the bore and base of the bullet, and that wouldn't be significant in this context. And then there is the friction as it goes down the bore.

Indeed maybe friction can cause the surface of a bullet to melt. The total amount of heat created by friction out a 20" barrel is mostly the same no matter how fast you push it. But the faster you push the boolit out, the more chance you can melt an extremely shallow outer layer of boolit before the heat can transfer to the core. Perhaps just a tiny layer of the surface might melt, but enough to allow a leak that will quickly consolidate into one big channel/gas-jet down the side of the bullet. Once this forms, the heat of the burning gases jetting by at 30k psi drops the hammer.

The check maybe continues to seal. But thicker and more copper in the gas check, the more it can provide cooling or heat-sinking to a leak that has already formed despite the check.

So I'm still stuck on gas leak as important to boolit failure for the reason check material and thickness should be important when pushing the limits of pressure and velocity.

[gloob]

I think leaks are just part of shooting boolits fast. A boolit is maybe like a boat that leaks and will eventually sink. The idea is to limit the leaks just long enough to make it through a very short trip. This is why lube grooves need a certain amount of lube in very much excess of what would be deposited into the pores of the barrel, should the lube groove remain sealed. There has to be enough lube to be melted and sprayed into the inevitable leaks, for this short trip.

[TD1886]

^Please be careful, there, Larry. Boyle's Law applies to gases, only. Liquids and solids are incompressible.

The only heat to the check that would be indirectly caused by pressure would be due to mechanical deformation/flow of the copper as the pressure formed it to the bore and base of the bullet, and that wouldn't be significant in this context. And then there is the friction as it goes down the bore.

Indeed maybe friction can cause the surface of a bullet to melt. The total amount of heat created by friction out a 20" barrel is mostly the same no matter how fast you push it. But the faster you push the boolit out, the more chance you can melt an extremely shallow outer layer of boolit before the heat can transfer to the core. Perhaps just a tiny layer of the surface might melt, but enough to allow a leak that will quickly consolidate into one big channel/gas-jet down the side of the bullet. Once this forms, the heat of the burning gases jetting by at 30k psi drops the hammer.

The check maybe continues to seal. But thicker and more copper in the gas check, the more it can provide cooling or heat-sinking to a leak that has already formed despite the check.

So I'm still stuck on gas leak as important to boolit failure for the reason check material and thickness should be important when pushing the limits of pressure and velocity.

Gloob you got me interested again plus some things Larry said. You're right about Boyle's Law. As far as pressure in the bore, after a certain point, it is decreasing as the volume of the bore increases farther along the bullet travels.

Like you I too would be more concerned with gas checks leaking. I really haven't seen real good evidence of this. What does amaze me is that as soft, or maybe better said "less strong" paper is on the base of a paper patched bullet that why the pressure doesn't deform that base? Even on flat base naked bases you don't see the deformation that you would think to be there. Yes , we do see the gas cutting.

Gloob I feel you are too concerned about gas checks conducting heat and not being strong enough for the job. Think of a heat sink. We're all familar with the aluminum heat sinks on electronic equipment. The are rather large compared to what they are cooling. Even the fins on air cooled engines have a lot of area. A gas check doesn't and I don't really think it's getting rid of much heat from the bullet or the powder combustion. Not enough to worry about.

I'm scratching my head thinking about Larry talking about melting the gas check shank and the check coming off. How does he obtain the accuracy he often talks about if that is happening?

[TD1886]

By the way one gram of powder produces about 3700 joules energy from high energy gun powder. There's is only one powder manufacturer that releases this type of data that I know of. You figure out who it is. While you are at figure out what the C or F degree of 3700 Joules is!!

[Larry Gibson]

"I'm scratching my head thinking about Larry talking about melting the gas check shank and the check coming off. How does he obtain the accuracy he often talks about if that is happening?"

I don't obtain nor claim the level of accuracy above 3,000 to 3,100 fps that I get at 2900 fps. That's where the GCs come off. Recovered such GCs show evidence of melted alloy inside the GC cup. Recovered bullets shot at 2900 fps show little sign of gas cutting or gas "leaking". BTW, the level of accuracy at 2900 fps is obtained in my 30x60 XCB rifle. It has a 31" barrel with a 16" twist. You're not going to get the same 1 - 1.5 moa accuracy with a sporter barreled 30-06 with a 10" twist......

gloob

"The only heat to the check that would be indirectly caused by pressure would be due to mechanical deformation/flow of the copper as the pressure formed it to the bore and base of the bullet, and that wouldn't be significant in this context. And then there is the friction as it goes down the bore."

I'm not talking about deformation of the GC. Talking about possible deformation of the much softer bullet GC shank. That's the only part that is melting and then not always with every bullet pushed above 50,000 psi/3000+ fps. If the heat to do that is from friction in the bore then how do you explain no melting of the bullet, no leading and only evidence of melting in recovered GCs is inside the GC?

Here's the recovered 30 XCB shot at 2900 fps with GCs, Not no alloy welded/soldered to the inside of the GCs.



Here's the remains of 2 Hornady GCs recovered from the inside of the Oehler Sky Screens. Note the alloy welded/soldered to the inside of the GCs. Both GCs and the Sky Screen housing were severely damaged......



Whatever we theorize the cause to be, the effect is still the same.

[gloob]

Gloob you got me interested again.

I'm glad I didn't put you off, yet. I know I am annoying, and I'm trying to improve on that.

As far as pressure in the bore, after a certain point, it is decreasing as the volume of the bore increases farther along the bullet travels.

Yep. An air compressor gets hot because it's compressing the air. But when you let the air back out, the air gets colder. It absorbs heat as it decompresses.

In a firearm, the powder releases energy in an exothermic reaction. So despite the pressure reducing back to normal, there is still a lot of heat.

Gloob I feel you are too concerned about gas checks conducting heat and not being strong enough for the job. Think of a heat sink. We're all familar with the aluminum heat sinks on electronic equipment. The are rather large compared to what they are cooling. Even the fins on air cooled engines have a lot of area. A gas check doesn't and I don't really think it's getting rid of much heat from the bullet or the powder combustion. Not enough to worry about.

The heatsink in a computer is dissipating heat by dissipating it to air. It has to take the heat being generated from a small point source and spread that out so that it contacts enough (room temperature) air to keep the cooling at a sufficient rate, continuously, even after it reaches steady state and the heatsink itself is now pretty darn hot. The gas check starts out cold to begin with. It's not going to dissipate that heat to anywhere except itself (except a little to the very surface of the boolit shank), so it doesn't need fins. It only has to absorb and spread out heat from the hot spots at the rim for the fraction of a second before the boolit exits.

It's like a tampon. Once it's saturated, it no longer works. But if it lasts long enough to do the job, that's all you need it to do. To be effective against a stronger, higher pressure leak, you need a bigger tampon.

[TD1886]

Larry

I'm not talking about deformation of the GC. Talking about possible deformation of the much softer bullet GC shank. That's the only part that is melting and then not always with every bullet pushed above 50,000 psi/3000+ fps. If the heat to do that is from friction in the bore then how do you explain no melting of the bullet, no leading and only evidence of melting in recovered GCs is inside the GC?

What you are seeing inside those gas checks tin that is part of the alloy make up of your bullet. Tin melts lower then all the rest of the alloys in mix. Friction from going the bullet going up the bore plus the heat from the powder combustion is what heats both the bullet and bore. I wasn't referring to friction heating the bore and bullet, I was referring to the friction yanking a case out of the chamber in a micr second, one which in many cases is still slightly obturated to the chamber walls.

I didn't think you were getting accuracy with those checks coming off and whatever is happening to the shanks.

Nobody answered why the pressure in the NRA full power loads (one's in the 50k bracket and over) wasn't deforming the base of the bullets when only paper protected them.

[TD1886]

I'm glad I didn't put you off, yet. I know I am annoying, and I'm trying to improve on that.


Yep. An air compressor gets hot because it's compressing the air. But when you let the air back out, the air gets colder. It absorbs heat as it decompresses.

In a firearm, the powder releases energy in an exothermic reaction. So despite the pressure reducing back to normal, there is still a lot of heat.



The heatsink in a computer is dissipating heat by dissipating it to air. It has to take the heat being generated from a small point source and spread that out so that it contacts enough (room temperature) air to keep the cooling at a sufficient rate, even after it reaches steady state and the heatsink itself is now pretty darn hot. The gas check starts out cold to begin with. It's not going to dissipate that heat to anywhere, so it doesn't need fins. It only has to absorb and spread out heat from the hot spots at the rim for the fraction of a second before the boolit exits.

It's like a tampon. Once it's saturated, it no longer works. But if lasts long enough to do the job, that's the goal.

Gloob I believe you meant when you let the air out of an air compressor it "cool"s by expanding. All gases that expand cool and some quite cold! That's the principle of how air conditioners work.

I'm sure the checks get plenty hot, you know thought I've never seen a fired recover check that wasn't still shiney. That is never seen them to have that annealed look and for that matter they were still harder then if they were annealed.

I believe that it is the friction of going through the air that a 220 Swift comes apart from the core melting. It's going about Mach 3.64 and plus you have the heat already in it from friction going down the bore and the powder gases burning.

[gloob]

...What does amaze me is that as soft, or maybe better said "less strong" paper is on the base of a paper patched bullet that why the pressure doesn't deform that base? Even on flat base naked bases you don't see the deformation that you would think to be there...

In this case, the path of least resistance must be the boolit to be accelerated more, rather than the base to deform. But for a relatively thin gas check with air between base of boolit and check, the check will be formed to the base of the bullet.

If the bullet is accelerated out the way, that increases the volume. That's what pressure does, it wants to expand. The only reason for the base of the bullet to be say cratered inward, deforming the entire bullet in order to create a tiny bit more volume, is if the friction was somehow really high between bullet and barrel to the point of an obstruction. And if that was the case, why would it stop there? The center of the bullet would just get blown out, leaving a donut of lead in the barrel. I bet you have a kB before that happens.

This is why a gas check shouldn't need "structural strength" anymore than PC or paper patching does.

[TD1886]

Larry here's a tip for you. Put a paper liner inside your gas check. It will insulate it from the shank. It won't interfere with the check. I've done this. See if this stops that melt inside the gas check.

[Larry Gibson]

Larry here's a tip for you. Put a paper liner inside your gas check. It will insulate it from the shank. It won't interfere with the check. I've done this. See if this stops that melt inside the gas check.

I suppose I could revisit 3000+ fps and try that but to what end other than seeing if it works? I'm quite satisfied with 2900 fps with the 30 XCB. That well proved my point with ternary alloyed, lubed cast bullets regarding the RPM Threshold, that properly designed and lubed cast bullets of the correct alloy do not strip in the rifling or lead the barrel at really high velocity and that 1 - 1 1/2 moa accuracy with 10 shots strings was possible to 600 yards. There isn't exactly a lot of shooters building HV cast bullet rifles so an actual need to find out isn't apparent. Besides, I've got so many other test irons in the fire right now w/o enough time to complete those in a timely manner.

[gloob]

Larry here's a tip for you. Put a paper liner inside your gas check. It will insulate it from the shank. It won't interfere with the check. I've done this. See if this stops that melt inside the gas check.

I predict this will just mean he loses accuracy even earlier or at lower velocity. If the entire check is reaching melting temp by the time the boolit exits, I say it's due to a significant hot spot or leak on the rim of the check and his boolit is already suffered significant gas cutting down the side. I think the boolit would not be accurate by this point, even if you had the paper in there to prevent the check from melting off.

In my prediction, the base of bullet (as a whole, or on average) would stay a bit cooler, overall, due to this paper. But the gas check would get hotter, faster, because it can't share some of the heat with the base of the boolit, anymore. And the gas cutting down the side would be worse, i.e. it would become detrimental to accuracy at a lower velocity/pressure.

If there is no leak at all, the gas check should not get hot enough to melt the boolit. 2900 fps maybe changes that game of course! But we generally see boolit failure from the side. The base of the boolit doesn't melt first. The base is buffered by a boundary layer. Where gas jets by is much closer to max temperature, and all the time. So in my thinking, you could say the gas check is there to protect the side of the bullet by sharing the damage/heat to itself and the rest of the base which doesn't normally fail.

edit: also just realized one potential reason a paper patch doesn't scorch or burn. It might ignite at similar temperature to melting point of boolit alloy, but it has to "cook" a bit before it burns. At that temp, the structures decompose first, before ignition. At high enough temp over ignition temp this might occur "instantly," but the surface of the lead will melt right as it reaches that temp and gets enough additional heat to phase change from solid to liquid, without any waiting. And with enough pressure and gas jet velocity, lead will perhaps get eroded out as it softens even before it reaches melting point.

[TD1886]

I predict this will just mean he loses accuracy even earlier or at lower velocity. If the entire check is reaching melting temp by the time the boolit exits, I say it's due to a significant hot spot or leak on the rim of the check and his boolit is already suffered significant gas cutting down the side. I think the boolit would not be accurate by this point, even if you had the paper in there to prevent the check from melting off.

In my prediction, the base of bullet (as a whole, or on average) would stay a bit cooler, overall, due to this paper. But the gas check would get hotter, faster, because it can't share some of the heat with the base of the boolit, anymore. And the gas cutting down the side would be worse, i.e. it would become detrimental to accuracy at a lower velocity/pressure.

If there is no leak at all, the gas check should not get hot enough to melt the boolit. 2900 fps maybe changes that game of course! But we generally see boolit failure from the side. The base of the boolit doesn't melt first. The base is buffered by a boundary layer. Where gas jets by is much closer to max temperature, and all the time. So in my thinking, you could say the gas check is there to protect the side of the bullet by sharing damage control with the rest of the base.

edit: also just realized one potential reason a paper patch doesn't scorch or burn. It might ignite at similar temperature to melting point of boolit alloy, but it has to "cook" a bit before it burns. At that temp, the structures decompose first, before ignition. At high enough temp over ignition temp this might occur "instantly," but the surface of the lead will melt right as it reaches that temp and gets enough additional heat to phase change from solid to liquid, without any waiting. And with enough pressure and gas jet velocity, lead will perhaps get eroded out as it softens even before it reaches melting point.

Thing is Larry did say that the check itself DID NOT MELT, he believes the bullet shank started to melt because he found some form of alloy inside the gas check. I presume it's the tin. Larry does like some extra tin in his alloy blends. Larry chime in if I'm wrong about that.

[TD1886]

I suppose I could revisit 3000+ fps and try that but to what end other than seeing if it works? I'm quite satisfied with 2900 fps with the 30 XCB. That well proved my point with ternary alloyed, lubed cast bullets regarding the RPM Threshold, that properly designed and lubed cast bullets of the correct alloy do not strip in the rifling or lead the barrel at really high velocity and that 1 - 1 1/2 moa accuracy with 10 shots strings was possible to 600 yards. There isn't exactly a lot of shooters building HV cast bullet rifles so an actual need to find out isn't apparent. Besides, I've got so many other test irons in the fire right now w/o enough time to complete those in a timely manner.

Larry would be interesting to know if you would do the test, but I ask how would you collect the gas check fragments if it doesn't work? BTW did you recover those bullets that all this happened too and if so was the shank indeed melted?

[TD1886]

I suppose I could revisit 3000+ fps and try that but to what end other than seeing if it works? I'm quite satisfied with 2900 fps with the 30 XCB. That well proved my point with ternary alloyed, lubed cast bullets regarding the RPM Threshold, that properly designed and lubed cast bullets of the correct alloy do not strip in the rifling or lead the barrel at really high velocity and that 1 - 1 1/2 moa accuracy with 10 shots strings was possible to 600 yards. There isn't exactly a lot of shooters building HV cast bullet rifles so an actual need to find out isn't apparent. Besides, I've got so many other test irons in the fire right now w/o enough time to complete those in a timely manner.

Larry I was shooting my Yugo 48 B 8mm Mauser, which is scoped, a few years ago. I was shooting the Lyman 323471 moving along at tad over 2000 fps. Certainly no speed demon as you XCB load. I had a Directv satelite dish up at a measure 500 yards. I was shooting at paper target and I had 4 cartridges left so I shot at the dish. This group isn't in MOA it's in actual inches and as you can see for that distance with a military rifle it's not shabby at all.

[gloob]

Thing is Larry did say that the check itself DID NOT MELT, he believes the bullet shank started to melt because he found some form of alloy inside the gas check. I presume it's the tin. Larry does like some extra tin in his alloy blends. Larry chime in if I'm wrong about that.

Of course it didn't melt. Copper melts at over 1900F. But the cooling effect is dependent on the differential, so when the check gets hotter it doesn't absorb as much heat from the gases. The barrel is cooling this jet of gas on its side. But the check is helping to cool those gases, as well. And when the check gets hot enough to melt the base, that's not good either.

A thicker check could absorb more heat, faster or longer, before it peters out and is "full."

[TD1886]

Of course it didn't melt. Copper melts at over 1900F. But the cooling effect is dependent on the differential, so when the check gets hotter it doesn't absorb as much heat from the gases. The barrel is cooling this jet of gas on its side. But the check is helping to cool those gases, as well. And when the check gets hot enough to melt the base, that's not good either.

A thicker check could absorb more heat, faster or longer, before it peters out and is "full."

Well Gloob I'm waiting on a reply from Larry if the found the bullet that check came off of to see whether the base melted a lot or not. I feel it may be the thin leaching out first as it has the lowest melting point.

I've pushed my 30-06 to limits with a cast 172 grain bullet which was every bit into the 50K bracket and I've never seen anything like that. Only time I've every seen alloy on a gas check is when that gas check pushed some leading out of the bore.

[gloob]

I feel like you still don't get what I'm saying. And I'm fine if you don't agree, but I wish you got it, first.

The base of a boolit doesn't melt (the side does). So the check, which covers the base, should not only not melt, it shouldn't reach the temperature that would even melt lead. The only way it reaches that temp, demonstrated by Larry's boolits, is because it sucked out heat from a jet of gas that would have otherwise contributed to melting the side of the boolit.