One shot! My brand new Panda bolt got a fairly significant ring when I loaded the first shot with 4227 rather than TAC.
Andy Cross
New member
That's a start
Boyles gas law is a start. As an optical engineer who majored in applied physicists I can vouch for the fact that hot abbrasive gasses are the main cause for errosion of the barrel throat. The reason the barrel doesn't get saturated with heat and turn white hot is that most metals are lousy at thermal energy transfer. That's why you can hold on to a meatl rod with your hand while the end is in the forge. The hot high pressure gasses actually melt the steel a few molecules deep every time a shot is fired and this metal then flows in the direction of the gasses. Hot metal is also abrasive.
The duration the barrel is subjected to this amount of heat simply isn't long enough to transfer enough energy to the material before the pressure begins to drop ie the projectile begins to move. The same principle applies to why you can pass your hand through a bunsen burner flame without getting blistered. But try holding it there for a couple of tenths of a second more and look out.
There are various other chemical forces at play that cause throat errosion as well but rest assured wear from frictional drag of projectiles travelling across the rifling although will contribute to it is inconsequential when compared with the hot abrassive gasses.
Andy
Boyles gas law is a start. As an optical engineer who majored in applied physicists I can vouch for the fact that hot abbrasive gasses are the main cause for errosion of the barrel throat. The reason the barrel doesn't get saturated with heat and turn white hot is that most metals are lousy at thermal energy transfer. That's why you can hold on to a meatl rod with your hand while the end is in the forge. The hot high pressure gasses actually melt the steel a few molecules deep every time a shot is fired and this metal then flows in the direction of the gasses. Hot metal is also abrasive.
The duration the barrel is subjected to this amount of heat simply isn't long enough to transfer enough energy to the material before the pressure begins to drop ie the projectile begins to move. The same principle applies to why you can pass your hand through a bunsen burner flame without getting blistered. But try holding it there for a couple of tenths of a second more and look out.
There are various other chemical forces at play that cause throat errosion as well but rest assured wear from frictional drag of projectiles travelling across the rifling although will contribute to it is inconsequential when compared with the hot abrassive gasses.
Andy
M
mks
Guest
The pressure drops to about 10,000 psi as the bullet exits, then drops to 14.7 quickly. Gay-Lussac's law is T2 = T1 * P2/P1. Plug in T1 = 3760R, P2 = 14.7 and P1 = 60,000 and you get T2 = 1R = -459F. Substitute P2 = 10,000 and you get T2 = 627R = 167F. If the powder were all burned up at the peak of the pressure pulse, this is what you would get. Of course it isn't, but Gay-Lussac helps explain why the throat is exposed to higher temperature than the muzzle.
Boyle's law relates pressure and volume: P2 = P1 * V1/V2
M
mks
Guest
Good one, Mike.
M
mike in co
Guest
not quite so...time is the culprut here....not much time but time as in ms.
as an example...
222 rem 24" bbl 52 gr bullet 4198 powder
pressure peaks at just under 50kpsi in a prox 0.3ms and at 0.1ms the bullet has left the bore BUT pressure at that time and point is aprox 400 PSI.....'quickly' is a vague term.
mike in co
as an example...
222 rem 24" bbl 52 gr bullet 4198 powder
pressure peaks at just under 50kpsi in a prox 0.3ms and at 0.1ms the bullet has left the bore BUT pressure at that time and point is aprox 400 PSI.....'quickly' is a vague term.
mike in co
goodgrouper
tryingtobeabettergrouper
Thanks Andy. Nice to see that other people study this stuff too to get their facts rather than just go off their own beliefs.
Even when you put the research up on the screen, some folks can't accept it. I guess you can lead a horse to water................
I thought this was pretty clear:
Erosion from Propellants (from Sierra ballistics)
With the passing of corrosive primers, erosion from the propellant itself is undoubtedly your barrel’s greatest enemy. When the powder is ignited, it creates extremely hot gases under tremendous pressure. These two factors combine to create erosion, particularly in the throat area of the barrel.
Some older powders, such as DG Pyro or Hi-Vel#2, were very erosive due to their high nitroglycerine content and the resulting high flame temperature. When the 1903 Springfield was first introduced, the original loading of a 220 grain round-nose bullet at 2200 fps gave a useful barrel life of only 800 rounds. This was due to the high nitroglycerine content and resulting high flame temperatures of the powders then in use. As powder chemistry has improved, longer barrel life has been achieved. However, erosion from propellants will probably remain the No. 1 factor in barrel wear in the foreseeable future. This situation is unlikely to change until some radical improvements are made in the chemical makeup of the powder.
Bullet Friction
Bullet friction, as it pertains to barrel wear, is frequently a topic of discussion among shooters. While this friction causes some wear, it is the least measurable factor in barrel life.
goodgrouper
tryingtobeabettergrouper
First of all, where did you get a muzzle pressure of 15 psi from? I said 15%, not 15 psi.
Secondly, 15% of 50,000 psi peak pressure would still leave enough muzzle pressure to vent through a brake. That's why the math works and we see gas venting.
Lastly, are you disagreeing that more surface area cools faster?
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goodgrouper
tryingtobeabettergrouper
M
mks
Guest
Never measured it myself. I got my info here: http://www.frfrogspad.com/intballi.htm
Seemed credible. If you have a better source, please let me know.
Thanks,
Keith
goodgrouper
tryingtobeabettergrouper
From Understanding Firearm Ballistics 6th edition, by Robert A Rinker
Pg 29 second paragraph
"Pressures of 55,000 psi are common at the peak but may drop to 6,000 psi by the time the bullet reaches the muzzle. With most powder, the flame temperature will reach about 5,550 degrees F at the peak pressure. Most barrel steel will melt at half that temp or about 2,500 F. The high temp peak will only last for a small fraction of a second and, with the exception of mahcine guns, will cool a lot between each shot".
This is talking about single base powder in normal conditions in small arms at peak pressures. Elsewhere, many studies average the temp from ignition to muzzle and get around the 3,000 or 3,500 degrees F. The combined time at which the temp stays at around 3,000 F is much longer than the peak temp of 5,500, so many places just use that number instead.
4
4Mesh
Guest
15 PSI is roughly what you are standing in right now. Ambient?
Plenty goes through a brake. Got no issue with that.
Surface area. All I laugh at is that somehow by you guys estimation, that surface does not help the brake get hot, but DOES help it to get cold. Damn interesting. More interesting is that inside the barrel, you have vastly less surface to heat with, yet, that gets hot in spite of having proportionately 2x or 3x the cooling area.
Because they have fluffy crap inside them that wears out, just like a muffler on a car. Just quicker. Typically, mesh of some sort.
Look, just read EXACTLY what it says above. No, the damn COPPER bullet does not cause significant wear. But grinding that Copper bullet along with the BURNT POWDER DOES. The FRICTION caused by the burnt powder is what causes the wear. They probably refer to gas, more because the "Gas" has precipitates which leave it during cooling and stick to the barrel. Just like the crap inside a stack pipe on a furnace.Thanks Andy. Nice to see that other people study this stuff too to get their facts rather than just go off their own beliefs.
Even when you put the research up on the screen, some folks can't accept it. I guess you can lead a horse to water................
I thought this was pretty clear:
Erosion from Propellants (from Sierra ballistics)
With the passing of corrosive primers, erosion from the propellant itself is undoubtedly your barrel’s greatest enemy. When the powder is ignited, it creates extremely hot gases under tremendous pressure. These two factors combine to create erosion, particularly in the throat area of the barrel.
Some older powders, such as DG Pyro or Hi-Vel#2, were very erosive due to their high nitroglycerine content and the resulting high flame temperature. When the 1903 Springfield was first introduced, the original loading of a 220 grain round-nose bullet at 2200 fps gave a useful barrel life of only 800 rounds. This was due to the high nitroglycerine content and resulting high flame temperatures of the powders then in use. As powder chemistry has improved, longer barrel life has been achieved. However, erosion from propellants will probably remain the No. 1 factor in barrel wear in the foreseeable future. This situation is unlikely to change until some radical improvements are made in the chemical makeup of the powder.
Bullet Friction
Bullet friction, as it pertains to barrel wear, is frequently a topic of discussion among shooters. While this friction causes some wear, it is the least measurable factor in barrel life.
This is the exact same discussion as "Finer threads are stronger". What a load of horses__. READ what was written. Not what you think was written. Why do you think they say, "This situation is unlikely to change until some radical improvements are made in the chemical makeup of the powder." That is because it is the dirt left behind that is not offering lubricity.
This whole thing make me laugh. Hell,there's people here who won't run a bronze brush down a stainless barrel for fear of wear, yet, a bullet grinding that powder in does virtually nothing. So wtf does a brush do?
When a round burns clean, it has virtually no throat wear. I've demonstrated this a few times. Now, how is it that if you don't produce dirt, the barrel doesn't wear out. But if you do, it does? How? Go back to post one. Same question. Why does one cartridge of otherwise similar spec (bullet dia/weight) cause more wear, dramatically. Well, because most of what was written about gas causing wear above is bs. That's why. Because the case with more propellant under less peak pressure with more initial volume causes more wear.
Seal the damn chamber, create MORE pressure, and the throat won't wear out.
M
mks
Guest
Thanks, looks like I should get Rinker's book.
Here's another factoid from Schaefer's website that is relevant to this discussion:
"According to The World s Great Rifles, by Roger Ford (1998, Brown Packaging Books, Ltd., London) it is estimated that just one-fifth of one percent of the energy produced when a cartridge is fired goes to rotating the bullet, while friction in the barrel accounts for another three percent, 20 to 30 percent goes to propelling the bullet, 30 percent goes in heat to the barrel, and 40 percent goes in muzzle blast."
If 30% of the energy in the powder is going into the barrel at temperatures as high as 5550F, seems like that could damage the steel.
Cheers,
Keith
Hovis like I've always ask shooters, do you think your cleaning rod or brush is doing as much damage as a bullet putting 60,000 lbs. pressure down the barrel? I don't think so! I think everyone is right it all has to do with wear, friction,dirt, heat, for every action there is a reaction.
Joe Salt
Joe Salt
M
mks
Guest
Sensible heat and kinetic energy.
Vern
Morethan1waytoskinacat
Not agreeing or disagreeing with anyone.
Take the really thin sporter barrels and fire a couple of shots,,, gets hot really fast, considerably different than the BR barrels we normally use.
What about (as was mentioned earlier) fire forming with wax and no bullet,,,, barrel gets hot fast too.
IF just IF it were just the dirt from the powder then Jerry Hensler's method of mixing moly (I think it was moly) with the powder (I believe he actually has a patent for this) seems to solve the dirt issue or I believe that was the result of his study.
Finally try taking a laser thermometer and measure the temp on various parts of the barrel after each shot and continue shooting 5-10 rounds.
Wait about 2 minutes and measure again after you finish the string.
Just things to consider....
Take the really thin sporter barrels and fire a couple of shots,,, gets hot really fast, considerably different than the BR barrels we normally use.
What about (as was mentioned earlier) fire forming with wax and no bullet,,,, barrel gets hot fast too.
IF just IF it were just the dirt from the powder then Jerry Hensler's method of mixing moly (I think it was moly) with the powder (I believe he actually has a patent for this) seems to solve the dirt issue or I believe that was the result of his study.
Finally try taking a laser thermometer and measure the temp on various parts of the barrel after each shot and continue shooting 5-10 rounds.
Wait about 2 minutes and measure again after you finish the string.
Just things to consider....
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