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Cheechako
Guest
Is anyone aware of any studies that have tried to measure the amount of barrel erosion due to bullet friction compared to the erosion due to the hot gasses?
Ray
Ray
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frwillia
Guest
Is anyone aware of any studies that have tried to measure the amount of barrel erosion due to bullet friction compared to the erosion due to the hot gasses?
Ray
No, but a borescope comparison of the throat which is bathed in hot gasses with the muzzle end of the barrel which isn't, at 500 round intervals with a borescope, might be instructive.
One can set a barrel back till there's no room for a chamber and the barrel near the muzzle, which pretty much only sees friction from the bullet moving it's fastest, is still not worn out.
Fitch
XBBR Shooter
New member
Is anyone aware of any studies that have tried to measure the amount of barrel erosion due to bullet friction compared to the erosion due to the hot gasses?
Ray
There is no "wear" from friction.
If there were... it would be the muzzle that went first.
Meow
There is no "wear" from friction.
If there were... it would be the muzzle that went first.
Meow
meow???
sounds like a Coburn to me
LOL
al
Boyd Allen
Active member
Maybe not bullet friction, but what about sand blasting by propellant particles? Those tend to go away farther up the barrel, where there flow may become more laminar as well.
Vern
Morethan1waytoskinacat
Not trying to start an argument here just some observations that might be wrong but logic dictates other wise.
Friction? IF the bore is the same diameter from one end to the other, then immediately after the bullet is compressed into the lands and grove the friction would be basically the same all the way down the rest of the barrel would it not? Or would the fact that the bullet is going to get hotter and hotter due to friction make some mathematical statement indicating more friction at the end or just more heat because of friction.
Heat? When you watch a gun fire at night flame or whatever you want to call it comes out of the end of the barrel so wouldnt heat be basically the same just past the throat? Or would it increase because of the friction of the bullet?
Lastly as a do your own test for heat.... fire 5-10 shots in rapid succession and use a digital laser thermometer to immediately check the heat of the barrel from end to end and continue to do so for several minutes and see where the hottest place is to start and where it is at the end.
Was it all the same? Was it hotter at the throat area or near the muzzle?
Just asking for real facts not opinions.
Friction? IF the bore is the same diameter from one end to the other, then immediately after the bullet is compressed into the lands and grove the friction would be basically the same all the way down the rest of the barrel would it not? Or would the fact that the bullet is going to get hotter and hotter due to friction make some mathematical statement indicating more friction at the end or just more heat because of friction.
Heat? When you watch a gun fire at night flame or whatever you want to call it comes out of the end of the barrel so wouldnt heat be basically the same just past the throat? Or would it increase because of the friction of the bullet?
Lastly as a do your own test for heat.... fire 5-10 shots in rapid succession and use a digital laser thermometer to immediately check the heat of the barrel from end to end and continue to do so for several minutes and see where the hottest place is to start and where it is at the end.
Was it all the same? Was it hotter at the throat area or near the muzzle?
Just asking for real facts not opinions.
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Cheechako
Guest
And real facts, Vern, are hard to come by which is why I asked. I know a lot of casual shooters who think that bullet friction wears out a barrel. I'm sure you guys know a lot of them too. I try to explain how it's the hot gasses, but I also realize, as Gerry said, that there must be some erosion due to friction. But how much is "some"? Judging by the condition of a shot out barrel at the muzzle, it would appear that "some" is very little, probably small enough to be insignificant. Another strong arguement to support heat erosion is the fact that you can also shoot out a throat without a bullet, such as when fire-forming. Maybe comparing two barrels, one shot out with bulleted loads, and another without bullets, could give some idea. But you'd probably have to have some very expensive measureing devices to tell.
I was sure that Al could answer my question. I'll bet he's working on it as we speak.
Ray
I was sure that Al could answer my question. I'll bet he's working on it as we speak.
Ray
Vern
Morethan1waytoskinacat
Ray I often wondered about the fire forming.
For most its done with a bullet but for me I do it with pistol powder and always wondered when I was having to do it with my only barrel if I was doing more harm than shooting bullets. However I fire form that way not because of the fear of wearing out the barrel but because I like to fire form then turn the necks and I can fire form right inside the house if I use a roll of insulation.
For most its done with a bullet but for me I do it with pistol powder and always wondered when I was having to do it with my only barrel if I was doing more harm than shooting bullets. However I fire form that way not because of the fear of wearing out the barrel but because I like to fire form then turn the necks and I can fire form right inside the house if I use a roll of insulation.
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Cheechako
Guest
Vern - Because fire-forming loads without a bullet are usually at a much lower pressure, the rate of erosion should be much slower. But you definitely have to pace yourself because the barrel can get just as hot as it does with bullets, which means that the hot gasses are at work. There are a lot of good reasons for not using a bullet, but avoiding barrel erosion is not one of them.
At least that is what I think. What do you guys say?
Ray
At least that is what I think.
What do you guys say?Ray
R
Roy Allain
Guest
Heat erosion is one way to describe it. However, it is actually much more than that. It is plasma erosion. As you know, upon firing, the burning powder generates heat & PRESSURE. This in turn becomes plasma, which is much, much hotter than just heat. Think of plasma welding/cutting. Just my .02 cents. Very good thread Ray.
Roy
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frwillia
Guest
The bullet, which is about the diameter of the grooves, is forced onto the lands. After that the friction should be relatively the same down the rest of the bore assuming the bore is exactly that size all the way to the muzzle, which it isn't. The bullet is, however, in contact with the surface with enough pressure to seal the high pressure gasses behind it. So there will be friction that contributes to barrel wear all the way down the barrel.
The temperature and pressure are much higher, about 5 times higher, at the throat than at the muzzle. Also, the bullet is moving much slower near the throat so the higher temperature and higher pressure have a longer exposure to the metal of the throat and the portion of the barrel just beyond then they do the metal farther down the bore. As the bullet moves down the bore it both accelerates and leaves an increasing volume behind it which causes the pressure and temperature of the gasses to drop and have less time to heat the metal. So no, the effect of temperature and pressure is not the same everywhere in the bore.
That test won't tell you much unless you are measuring the temperature of a barrel that is the same diameter from end to end.
The mechanism of thermal shock erosion which is what is happening in the throat is much more damaging to the barrel than the friction of the copper jacketed bullet on the internal bore surfaces. That is, quite simply, why the barrel wears out in the throat first.
Fitch
Well.....
Last nite I chambered up a straight contour blank with a chamber on each end.
I inserted one of my experimental air-charge cartridges that I'd drilled and tapped for 1/4X28.................. on each end.
I grated the end of each air-case.....
I stuck a rocker valve in the middle, slugged up a bullet and fah'red 'er up about 11:30 last nite. It's had a bullet clacking back and forth now for over 20hrs, no discernable change.
I'll air gage it on 20 days...
al
Last nite I chambered up a straight contour blank with a chamber on each end.
I inserted one of my experimental air-charge cartridges that I'd drilled and tapped for 1/4X28.................. on each end.
I grated the end of each air-case.....
I stuck a rocker valve in the middle, slugged up a bullet and fah'red 'er up about 11:30 last nite. It's had a bullet clacking back and forth now for over 20hrs, no discernable change.
I'll air gage it on 20 days...
al
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Cheechako
Guest
Now that is a test! Well thought out. Indisputable results. I can't hardly wait until June 23 to learn how much wear you can measure on the barrel, the bullets, the rocker valve, and the nerves of your family and neighbors after 20 days of clacking.
Ray
Ray
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frwillia
Guest
Al, I haven't had that good a laugh for days. I managed not to spill my coffee, or spray it all over the monitor, but barely.
That was great! Thanks a bunch!
Fitch
Vern
Morethan1waytoskinacat
The bullet, which is about the diameter of the grooves, is forced onto the lands. After that the friction should be relatively the same down the rest of the bore assuming the bore is exactly that size all the way to the muzzle, which it isn't. The bullet is, however, in contact with the surface with enough pressure to seal the high pressure gasses behind it. So there will be friction that contributes to barrel wear all the way down the barrel.
That is about what I expected
The temperature and pressure are much higher, about 5 times higher, at the throat than at the muzzle. Also, the bullet is moving much slower near the throat so the higher temperature and higher pressure have a longer exposure to the metal of the throat and the portion of the barrel just beyond then they do the metal farther down the bore. As the bullet moves down the bore it both accelerates and leaves an increasing volume behind it which causes the pressure and temperature of the gasses to drop and have less time to heat the metal. So no, the effect of temperature and pressure is not the same everywhere in the bore.
Makes sense to me
The mechanism of thermal shock erosion which is what is happening in the throat is much more damaging to the barrel than the friction of the copper jacketed bullet on the internal bore surfaces. That is, quite simply, why the barrel wears out in the throat first.
As I suspected and why I worried. This MIGHT account for why some guys who shoot the lower nodes seem to say their barrels last longer than guys who shoot on the very edge of the top node
Which brings me to another question or 2.
6mm and 30 cal. Are the pressures about the same on hot loads? I dont know thats why I am asking.
If so why is it claimed by so many that 30br barrels last so much longer?
That is about what I expected
The temperature and pressure are much higher, about 5 times higher, at the throat than at the muzzle. Also, the bullet is moving much slower near the throat so the higher temperature and higher pressure have a longer exposure to the metal of the throat and the portion of the barrel just beyond then they do the metal farther down the bore. As the bullet moves down the bore it both accelerates and leaves an increasing volume behind it which causes the pressure and temperature of the gasses to drop and have less time to heat the metal. So no, the effect of temperature and pressure is not the same everywhere in the bore.
Makes sense to me
The mechanism of thermal shock erosion which is what is happening in the throat is much more damaging to the barrel than the friction of the copper jacketed bullet on the internal bore surfaces. That is, quite simply, why the barrel wears out in the throat first.
As I suspected and why I worried. This MIGHT account for why some guys who shoot the lower nodes seem to say their barrels last longer than guys who shoot on the very edge of the top node
Which brings me to another question or 2.
6mm and 30 cal. Are the pressures about the same on hot loads? I dont know thats why I am asking.
If so why is it claimed by so many that 30br barrels last so much longer?
Boyd Allen
Active member
The ratio of the bore to the case volume is such that the total volume behind the bullet increases at a much higher rate so the pressure drops faster. Also, the heat of combustion is distributed to and cooled by a larger surface area. Do I absolutely know these are the reasons? No, they are just my best guess. Anybody else?
Because no one has brought up what effects twist rate might play into the equation.
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friction and wear
Contact pressure, which determines friction, is a function of yield strength of the bullet metal and the pressure applied to the base of the bullet. Strength of bullet is same from breech to muzzle, but base pressure is higher at breech, so total contact pressure, and thus friction, starts off high at breech and then drops off at muzzle. Temperature is higher at breech so this together with the higher friction is why wear is higher at breech.
True contact between bullet surface and bore surface consists of zillions of small "hills and valleys" rubbing against each other. The soft hills of copper or lead will usually just push over or deform the hills of steel - which results in "polishing" or "burnishing". Sometimes though the steel hills are broken or sheared off which results in a particle - this we call "wear". Sometimes that loose particle will roll around between the surfaces and cause more wear. If you can get a "lubricant" (oil, graphite, molydi, almost any particle) between the surfaces you will probably reduce friction and wear.
However, when the copper wear particles, and the copper that is adhering to the bore are removed after cleaning, wear of bore might be intensified. The fewer shots fired between cleaning, the more the wear may be increased. In other words cleaning may shorten barrel life.
Contact pressure, which determines friction, is a function of yield strength of the bullet metal and the pressure applied to the base of the bullet. Strength of bullet is same from breech to muzzle, but base pressure is higher at breech, so total contact pressure, and thus friction, starts off high at breech and then drops off at muzzle. Temperature is higher at breech so this together with the higher friction is why wear is higher at breech.
True contact between bullet surface and bore surface consists of zillions of small "hills and valleys" rubbing against each other. The soft hills of copper or lead will usually just push over or deform the hills of steel - which results in "polishing" or "burnishing". Sometimes though the steel hills are broken or sheared off which results in a particle - this we call "wear". Sometimes that loose particle will roll around between the surfaces and cause more wear. If you can get a "lubricant" (oil, graphite, molydi, almost any particle) between the surfaces you will probably reduce friction and wear.
However, when the copper wear particles, and the copper that is adhering to the bore are removed after cleaning, wear of bore might be intensified. The fewer shots fired between cleaning, the more the wear may be increased. In other words cleaning may shorten barrel life.
JerrySharrett
Senile Member
Throwing another clod in this churn of barrel erosion brings up the question of why does a benchrest barrel lose accuracy between cleanings. I suggest the powder and copper fouling change the vibration pattern from what existed in the clean bore.
AND, will this additional fouling reduce or increase barrel erosion? I think thousands of rounds rapidly fired at prairie dogs proves heat is a factor of accelerated erosion, but does the fouling its self increase or reduce erosion? In earlier days I've "shot out" a couple of barrels in one day!!
AND, will this additional fouling reduce or increase barrel erosion? I think thousands of rounds rapidly fired at prairie dogs proves heat is a factor of accelerated erosion, but does the fouling its self increase or reduce erosion? In earlier days I've "shot out" a couple of barrels in one day!!