Burning Powder
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mike in co
Registered User
goodgrouper
tryingtobeabettergrouper
I think you're looking at it the wrong way. The brake is further from the heat. It starts out colder and ends up colder. The barrel gets hotter because it's taking the majority of the heat.
I don't buy that. You can look down any barrel and see there is more "dirt" (as you call it) on the bottom. Therefore, we'd expect to see more wear on the bottom. But when we take borescopes and look into the throat, we see wear 360 degrees around the throat in even pattern. Research the pressure wave that is ahead of the bullet sometime. Unburnt powder doesn't stand a chance of being "run over" by an approaching bullet. Much less a bullet that is swaged out to the bore walls....
Wrong. They said that in a context about chemicals and their erosion properties. Not about "dirt"! In comparing single base powders to double base; nitroglycerin vs. nitrocellulose chemical makeup.
Agreed. Brushing ain't hurting a thing. Simple borescope shows that.
I'd sure like to know how!
I'd sure like to see your sources of information on that. Come to think of it, so would everybody else who's ever tried to get more barrel life out of a piece of steel with modern propellant! You need to package this claim and make your billions! The military alone would buy into it for their machine gun barrels that they have to keep replacing. No more testing of porcelain lined barrels. Just crank up the pressure and that barrel will last forever! Honestly Mesh, I've heard some doozies on many gun forums, but I think you just took the cake my friend!!! You're going to make Mikey look like Einstein here if you're not careful!
Doug Casner
New member
You guys are talking way over my head but Ive got a .257 weatherby that lost its accuracy in less than a 1000 rounds. I can see how funneling all that gas through a little hole would build up heat fast. It has a thin barrel too. You guys said it so an old country boy could understand. Im not into alligatoring but I dont live in Fla.
Vern
Morethan1waytoskinacat
Joe you just made me think (ouch).
One of those what if moments....
What if you had a nozel on one of those high powered water jets that was the same dimension as a ppc case.
Stuck a bullet on the end of it shoved it into a barrel and used water pressure to send the bullet on its merry little way.
We would eventually have barrel wear.
Where would the wear be?
Like we see now mostly ahead of the chamber where the most pressure would be?
Or would there be uniform wear down the length of the barrel?
One of those what if moments....
What if you had a nozel on one of those high powered water jets that was the same dimension as a ppc case.
Stuck a bullet on the end of it shoved it into a barrel and used water pressure to send the bullet on its merry little way.
We would eventually have barrel wear.
Where would the wear be?
Like we see now mostly ahead of the chamber where the most pressure would be?
Or would there be uniform wear down the length of the barrel?
Bob Kingsbury
New member
I have no doubt that everything mentioned contributes to barrel erosion. I do however wonder why our cases last as well as
they do. Given a PPC case, with .008 thick necks and at the time of firing, sit within .030 of all this damage. I have cases that
have seen 70 firings, yet no erosion , gas cutting( leakage around bullet) or abrasion from all the crap that rushes out the
little funnel we call the neck. Its agreed that 70 or so firings is not the 1500-3000 that ends a barrels life. It should however show some signs , since brass melts way before steel. Were it not for the brass changing its properties, we could shoot them forever.
What I'm getting at, is that whatever occurs in the throat, also happens in the neck. Why do bolt faces pit, but leakage from
primers causes less damage to the brass.
they do. Given a PPC case, with .008 thick necks and at the time of firing, sit within .030 of all this damage. I have cases that
have seen 70 firings, yet no erosion , gas cutting( leakage around bullet) or abrasion from all the crap that rushes out the
little funnel we call the neck. Its agreed that 70 or so firings is not the 1500-3000 that ends a barrels life. It should however show some signs , since brass melts way before steel. Were it not for the brass changing its properties, we could shoot them forever.
What I'm getting at, is that whatever occurs in the throat, also happens in the neck. Why do bolt faces pit, but leakage from
primers causes less damage to the brass.
Because brass is a better conductor.
Andy Cross
New member
He's correct
He's correct. The brass case is surrounded by a thing called a heat sync otherwise known as the barrel. The brass gets hot but it's a good conductor and the heat is directed away from it. The powder actually burns at a lower temperature in the case but increases in flame temperature as it expands out of the case becuase more molecular movement is possible and therefore more energy can be released. Brass cases fail mainly due to metal fatigue. When and where they fail is difficult to determine and will vary from one batch of metal to the next and on the manufacturing methods used to make them.
As far as the water jet propulsion idea the wear would probably occur at the entry end as the high pressure water flows from the reservior into the restriction of the barrel and again but to a lesser degree at the muzzle. The friction of water is greater than you might think.
Andy.
He's correct. The brass case is surrounded by a thing called a heat sync otherwise known as the barrel. The brass gets hot but it's a good conductor and the heat is directed away from it. The powder actually burns at a lower temperature in the case but increases in flame temperature as it expands out of the case becuase more molecular movement is possible and therefore more energy can be released. Brass cases fail mainly due to metal fatigue. When and where they fail is difficult to determine and will vary from one batch of metal to the next and on the manufacturing methods used to make them.
As far as the water jet propulsion idea the wear would probably occur at the entry end as the high pressure water flows from the reservior into the restriction of the barrel and again but to a lesser degree at the muzzle. The friction of water is greater than you might think.
Andy.
mike in co
Registered User
well i agree with most of what you said,,,,,but look at any pc of software and you will see the bullet has barely moved at peak pressure( also peak burn)...so the case sees alot of pressure, but is confined by the chamber, the bolt and thicker brass at its base, and the temp is there, but as has been pointed out, the heat does not stay, the xxxkpsi pressure keeps the brass in contact with the chamber walls and the heat is transfered.....
i think if one pc of brass could be fired 20 time in one min, we would see some brass failure..but it is an unlikely event.
mike in co
i think if one pc of brass could be fired 20 time in one min, we would see some brass failure..but it is an unlikely event.
mike in co
Bob Kingsbury
New member
That brass cases transfer heat to the barrel is easily demonstrated by the fact that cases during fireforming come out hot, whereas
cases FL sized or neck sized don,t. There is however sufficient abrasive crud in the powder to cause erosion, no different than
the nozzle of a sand blaster. If its abrasion in the throat, the mouth of the case sees this as well.--IMO
cases FL sized or neck sized don,t. There is however sufficient abrasive crud in the powder to cause erosion, no different than
the nozzle of a sand blaster. If its abrasion in the throat, the mouth of the case sees this as well.--IMO
dk hunt 14
New member
If heat is the major source of wear; why is the bottom of the throats worn more? In all the match barrels i bore scoped the bottom seems always to have more wear.
Fun with numbers...
If 3% of the energy is spent on bore friction, and if you're using a 60,000 psi load, total pressure variation do to friction is a maximum of 1,800 psi.
OK, suppose your bullet bearing surface is 1/2 inch (long range bullets). Suppose too that the bearing surface varies by .030. That's six percent, right? .5 divided by .030, Now 6% of 1,800 is is 108 psi. Actually, we should be talking area, not just length. That would give a smaller number, right?
108 psi is enough variance to sort bullets by bearing length? And some guys sort not by 30 thousandths, but 2 thousandths! That's .4%, or a 7.2 psi variance. How much energy is there is in burning a kernel of powder?
OK Keith, my math was never the best, never mind the likely conceptual error thinking this way. Where have I gone wrong?
If 3% of the energy is spent on bore friction, and if you're using a 60,000 psi load, total pressure variation do to friction is a maximum of 1,800 psi.
OK, suppose your bullet bearing surface is 1/2 inch (long range bullets). Suppose too that the bearing surface varies by .030. That's six percent, right? .5 divided by .030, Now 6% of 1,800 is is 108 psi. Actually, we should be talking area, not just length. That would give a smaller number, right?
108 psi is enough variance to sort bullets by bearing length? And some guys sort not by 30 thousandths, but 2 thousandths! That's .4%, or a 7.2 psi variance. How much energy is there is in burning a kernel of powder?
OK Keith, my math was never the best, never mind the likely conceptual error thinking this way. Where have I gone wrong?
Only two reasons I can think of...
Hot air rises, and that would mean there must be an equal and opposite reaction. Therefore, the bottom would receive more wear. Or maybe, pressure weighs a lot, and so with all that pressure, it would push harder on the bottom lands and wear them more. It could not possibly have to do with the dirt (carbon) laying in there. See! I'm reformed and convinced now. And just cause every gunsmith since the dawn of time has observed this, clearly something mysterious causes it. Not the obvious.
In fact, I believe this statement was refuted long ago in the thread.
I never noticed any such thing, and don't remember anyone else saying as much. In fact, I have only ever heard the opposite. But, since I read it here, it must be true.
Then this:
Wth do you guys think is going on. This is heat, you're talking abut, not electricity. (not that it would matter). So, a brass case conducts heat of 5000F through it in a matter of .01 milliseconds? Transfers that heat does it? Huh. I have annealed more than a few cases, and I can use a .850 length shellholder, heat the SHOULDER of the case to red hot, and still take it from the holder with my ungloved fingers. It didn't conduct that heat in FOUR - 4.5 seconds of time in the flame. But, OH, I forgot, pressure is magic and so under pressure, the heat will transfer won't it? Fascinating stuff here!
I am dying to hear how throat wear on the bottom is explained by heat and pressure. I'd also like to know how it is that this heat is gone because of the decrease in pressure, yet the end of a barrel typically gets just as hot as the breech. BUT, muzzle brakes don't get hot at all, in spite of flames going through them... And all is explained above
Oh, one more. Could someone explain why cases ejected from a gas gun are hotter than those from a centerfire? Even the very first round from a gas gun, ejects very hot brass. Didn't have time to conduct heat away I bet
Charles,
These order of magnitude or "ball park" calculations can be very useful, particularly for identifying factors that may make a difference. It's important to have a threshold to compare to. For 1000 yd shooting, the bullet drops about 500", right? A factor would be important if it changed drop by say 0.5" or 0.1%. An order of magnitude less, 0.01%, we would call insignificant. If a kernel of powder weighs 0.02 grains and your load is 40 grains, that's 0.05%, so that's significant.
For bearing friction, the 25% of the pressure that ends up propelling the bullet would be 15 kpsi, so the 0.002" variance in bearing length would change that pressure by 7.2/15k = 0.05%. That's significant, too.
Changing a 0.5 BC by more than 0.00005 would be significant. At 1000 yd, it's difficult to find things that are NOT potentially significant.
Cheers,
Keith
More like 70-80 grains powder. But a kernel weighs more like .03 or .04 grains, too
That 25% isn't all expended on friction. There is an air column to move, too. And the rate of acceleration is, for a while anyway, being increased.
Has anyone really ever done the math to see just what the frictional focre is, say, for a .30 with a 210 Berger -- seems a popular combination, these days...
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goodgrouper
tryingtobeabettergrouper
Ok Mesh. Enough of the rhetoric. Please!
Those of us who can put a little faith in scientific tests and published data have posted it here for anyone who wants to learn about it. We've given you the equations, the links, and the physics. We've even heard from professionals who studied this stuff. Yet, you continue to deny all of it for reasons that can only be guessed as chosen ignorance. Unless you can provide some research or data of your own supporting your claims, I think this thread is done. I'm tired of showing the horse where the water is. I want the horse to find a spring of his own....................
Those of us who can put a little faith in scientific tests and published data have posted it here for anyone who wants to learn about it. We've given you the equations, the links, and the physics. We've even heard from professionals who studied this stuff. Yet, you continue to deny all of it for reasons that can only be guessed as chosen ignorance. Unless you can provide some research or data of your own supporting your claims, I think this thread is done. I'm tired of showing the horse where the water is. I want the horse to find a spring of his own....................