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Barrel wear

nemesisenforcernemesisenforcer Member Posts: 10,513 ✭✭✭
is most barrel wear caused by gas cutting or jacketed bullet on bore friction?

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    charliemeyer007charliemeyer007 Member Posts: 6,579 ✭✭✭
    edited November -1
    I think high temperature gases do the most damage. Ball powder can have an advantage in barrel life.
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    MIKE WISKEYMIKE WISKEY Member, Moderator Posts: 9,988 ******
    edited November -1
    "is most barrel wear caused by gas cutting ".........for sure, bullets (copper or lead) cause VERY little wear. the old 'rule of thumb' is a barrel will last for 40 lbs. of powder.
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    noyljnoylj Member Posts: 172 ✭✭✭
    edited November -1
    Big difference in barrel wear between .45 Auto and .240 Weatherby Magnum, so high pressure and hot gasses.
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    nemesisenforcernemesisenforcer Member Posts: 10,513 ✭✭✭
    edited November -1
    quote:Originally posted by MIKE WISKEY
    "is most barrel wear caused by gas cutting ".........for sure, bullets (copper or lead) cause VERY little wear. the old 'rule of thumb' is a barrel will last for 40 lbs. of powder.


    Hadn't heard that, but it makes some sense. I'll keep that in mind.
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    JustCJustC Member Posts: 16,056 ✭✭✭
    edited November -1
    most "burned out" barrels suffer from throat erosion, not from rifling wear. Consider this,..a barrel that is a straight 1.25" dia from chamber to muzzle, can be cut off at the receiver end, re-threaded and re-chambered, and be right back in working fashion. This can't be done with most factory barrels since there isn't enough dia past the chamber as they come from the factory.

    sloppy cleaning from the muzzle end can cause degraded accuracy, but can be cleaned up by trimming and re-crowning.
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    SoreShoulderSoreShoulder Member Posts: 3,138 ✭✭✭
    edited November -1
    quote:Originally posted by JustC
    most "burned out" barrels suffer from throat erosion, not from rifling wear. The rifling wear would be worst at the throat because that's where the bullet is being engraved. Heat from the powder and from the friction of bullets already fired would make the metal at the origin of the lands more wear prone.
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    wanted manwanted man Member Posts: 3,276
    edited November -1
    quote:Originally posted by SoreShoulder
    quote:Originally posted by JustC
    most "burned out" barrels suffer from throat erosion, not from rifling wear. The rifling wear would be worst at the throat because that's where the bullet is being engraved. Heat from the powder and from the friction of bullets already fired would make the metal at the origin of the lands more wear prone.


    The erosion is the worst at the throat because that is where you are basically applying a plasma torch to the rifling every time you touch off a round, moreso if you are running "hot" home-rolled loads.........As usual, JustC hit the nail on the head
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    SoreShoulderSoreShoulder Member Posts: 3,138 ✭✭✭
    edited November -1
    quote:Originally posted by wanted manThe erosion is the worst at the throat because that is where you are basically applying a plasma torch to the rifling every time you touch off a round, moreso if you are running "hot" home-rolled loads.........As usual, JustC hit the nail on the head
    Can erosion be worse at the throat due to more than one factor?
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    Hawk CarseHawk Carse Member Posts: 4,374 ✭✭✭
    edited November -1
    Yes.
    High-nitroglycerine double base powders like Cordite and Hi-Vel No 2 are considered to be more erosive than straight nitrocellulose.

    Bruce Hodgdon always maintained that Ball powders were less erosive than extruded, but nobody will back him up.
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    jonkjonk Member Posts: 10,121
    edited November -1
    One country, I think Switzerland, did an experiment, where they fitted a rifle barrel to a special compressed air tank that produced the same pressure as one of their service rounds. They fired a ton of projectiles through it, and reached the conclusion that there was virtually no wear, ergo all wear must come from the gas cutting.
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    JustCJustC Member Posts: 16,056 ✭✭✭
    edited November -1
    the erosion at the throat, as already stated, is due to the plasma exiting the case mouth. This can be evidenced by employing the use of a bore scope. You will notice the alligator-skin look to the metal, which is known as "fire cracking", like a scortched earth.
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    SoreShoulderSoreShoulder Member Posts: 3,138 ✭✭✭
    edited November -1
    quote:Originally posted by jonk
    One country, I think Switzerland, did an experiment, where they fitted a rifle barrel to a special compressed air tank that produced the same pressure as one of their service rounds. They fired a ton of projectiles through it, and reached the conclusion that there was virtually no wear, ergo all wear must come from the gas cutting.
    This is not the experts forum so I am entitled to my guesswork.

    Five factors are not present with compressed air.

    The heat of firing may anneal the very surface of the origin of the rifling, leading to reduced wear resistance. The air test would not show this unless the barrel were heated between shots with a non-erosive method such as a laser beam which affected the very surface of the barrel, right where it gets hottest in real firing.

    Heat itself can affect the amount the barrel wears even if the very surface had never been exposed to temperatures which could anneal it slightly. Compressed air expanding would keep the barrel cool.

    In the real world, bullets may have grit on them.

    Copper fouling may have protected the origin of the lands, firing would have shot it off, if it can erode the very steel.

    The lube situation may be different. Bullets may have had a remnant of forming lube, which firing may blast off as hot gases race around the bullet before it's fully engraved into the throat. The gas flow may or may not be too fast to allow it to be replaced with graphite.

    What this adds up to is that a different bullet may wear the throat less. A bullet with a shorter shank or thinner jacket may wear the POSSIBLY heat softened metal less. It would create less frictional heating and maybe leave the metal more resistant to gas erosion. Grit would not be as bad with a short shank. And, by sealing the bore sooner or not lingering in the throat so long, with hot gases racing around an imperfect seal, it may reduce how hot the throat steel is before it has to take the full blast of the powder.
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    nemesisenforcernemesisenforcer Member Posts: 10,513 ✭✭✭
    edited November -1
    quote:Originally posted by SoreShoulder
    quote:Originally posted by jonk
    One country, I think Switzerland, did an experiment, where they fitted a rifle barrel to a special compressed air tank that produced the same pressure as one of their service rounds. They fired a ton of projectiles through it, and reached the conclusion that there was virtually no wear, ergo all wear must come from the gas cutting.
    This is not the experts forum so I am entitled to my guesswork.

    Five factors are not present with compressed air.

    The heat of firing may anneal the very surface of the origin of the rifling, leading to reduced wear resistance. The air test would not show this unless the barrel were heated between shots with a non-erosive method such as a laser beam which affected the very surface of the barrel, right where it gets hottest in real firing.

    Heat itself can affect the amount the barrel wears even if the very surface had never been exposed to temperatures which could anneal it slightly. Compressed air expanding would keep the barrel cool.

    In the real world, bullets may have grit on them.

    Copper fouling may have protected the origin of the lands, firing would have shot it off, if it can erode the very steel.

    The lube situation may be different. Bullets may have had a remnant of forming lube, which firing may blast off as hot gases race around the bullet. The gas flow may be too fast to allow it to be replaced with graphite.

    What this adds up to is that a different bullet may wear the throat less. A bullet with a shorter shank or thinner jacket may wear the POSSIBLY heat softened metal less. It would create less frictional heating and maybe leave the metal more resistant to gas erosion. Grit would not be as bad with a short shank. And, by sealing the bore sooner or not lingering in the throat so long, with hot gases racing around an imperfect seal, it may reduce how hot the throat steel is before it has to take the full blast of the powder.






    Even if your hypothesis is true, it reinforces, not undermines the hot gas at the throat analysis above.
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    SoreShoulderSoreShoulder Member Posts: 3,138 ✭✭✭
    edited November -1
    quote:Originally posted by nemesisenforcer[/iEven if your hypothesis is true, it reinforces, not undermines the hot gas at the throat analysis above.
    It would suggest that different bullets may wear the barrel differently.
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    JustCJustC Member Posts: 16,056 ✭✭✭
    edited November -1
    there is no such thing as annealing the throat. Annealing means softening the metal,....which is why you anneal brass case necks, so that they can be sized to hold a more consistent neck tension.

    IF, annealing the barrel throat were to ever happen,..the throat in the barrel would be eroded in 200-300rnds, and the barrel would need to be replaced. Annealing takes place at some 600-700* on brass,....steel is a whole nother story.

    Bullets with "grit" on them are either dropped in the dirt, and not cleaned off before chambering, or those garbage "fire lapping" rounds sold by folks who play on the lack of internal balistic knowledge of most folks.
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    SoreShoulderSoreShoulder Member Posts: 3,138 ✭✭✭
    edited November -1
    quote:Originally posted by JustC
    there is no such thing as annealing the throat. Annealing means softening the metal,....which is why you anneal brass case necks, so that they can be sized to hold a more consistent neck tension.

    IF, annealing the barrel throat were to ever happen,..the throat in the barrel would be eroded in 200-300rnds, and the barrel would need to be replaced. Annealing takes place at some 600-700* on brass,....steel is a whole nother story.The gases inside the case are incandescent and hot enough to melt the barrel, yet without benefit of experiment you can say for certain that NO PART of the barrel, not even the top layer of molecules on the ball seat of the lands facing the case mouth, reaches annealing temp, even after long shot strings.

    If the WHOLE barrel were annealed, it would need replacing in 200-300 rounds or so, but if a SMALL PART of the barrel were A LITTLE annealed then maybe it would wear A LITTLE more than a test with cold bullets and compressed air would show.

    I bet that test barrel had frost on it from all the compressed air expanding.
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    SoreShoulderSoreShoulder Member Posts: 3,138 ✭✭✭
    edited November -1
    quote:Originally posted by JustCBullets with "grit" on them are either dropped in the dirt, and not cleaned off before chambering, ...Bullets with A LOT of "grit" on them are dropped in the dirt, but it's just possible that a round or two has a particle or two on it every now and then. You never had any dust on anything after a hunt or a day at the range, not even one piece of sand that worked its way out of a concrete shooting bench, no matter how small, no matter how hard the wind blew?
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    JustCJustC Member Posts: 16,056 ✭✭✭
    edited November -1
    I don't typically shoot in the wind, since it is a waste of time for accuracy work and load testing, thus no sand blown into the throat of my barrel. My action is closed, even when no rounds are chambered. I also carry coated cleaning rods with me, in case I feel the need to poke the bore. My rods are always wiped down their entire length with a rag prior to entering my barrels. I am particular in this area, since I have many barrels that by themselves are anywhere from $550-$700 depending on make and whether they have brakes installed. That kind of attention naturally extends itself into my treatment of even factory barrels that I work with. I strive to eliminate variables, which makes me somewhat finicky in how I approach a range/load ladder situations. Most of these sessions are conducted from my benches inside an old hog house located on one of the properties I am allowed to hunt/shoot.

    here is one of a few sights I found courtesy of google, that discusses annealing steel.

    http://www.zianet.com/ebear/metal/heattreat5.html

    judging by the description of using a fire-box and excluding air from the process, I can't see how even a long shot string of overbore magnums could create enough temperature, throughout the barrel's thickness, while not having the air inside the bore, negate the heating process inside the bore at the throat in front of the chamber. The exiting plasma is dissipated in milliseconds as it is constantly expanding and becoming less dense, as the projectile is moving toward the muzzle, and thus is increasing the internal volume of the compression chamber which is the barrel chamber and bore behind that projectile.
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    SoreShoulderSoreShoulder Member Posts: 3,138 ✭✭✭
    edited November -1
    quote:Originally posted by JustCjudging by the description of using a fire-box and excluding air from the process, I can't see how even a long shot string of overbore magnums could create enough temperature, throughout the barrel's thickness, while not having the air inside the bore, negate the heating process inside the bore at the throat in front of the chamber. The exiting plasma is dissipated in milliseconds as it is constantly expanding and becoming less dense, as the projectile is moving toward the muzzle, and thus is increasing the internal volume of the compression chamber which is the barrel chamber and bore behind that projectile.
    So....it can burn the steel away, but not soften it a little.

    OK.

    You need a bunch of stuff for a good, even anneal...therefore, no softening ever happens under any different circumstances, ever.
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    JustCJustC Member Posts: 16,056 ✭✭✭
    edited November -1
    erosion and annealing are very different things. Notice where the article states that not allowing the steel to cool too quickly is paramount to annealing (thus eliminating the oxygen) so as not to allow hardening of the metal (the opposite of annealing[;)]). And since you have air immediately in contact with the surface of the throat, after firing (where it never reached the "glowing" temperature in the first place), you are either hardening the steel, or not affecting it either way.

    an annealed metal doesn't resemble alligator skin,..eroded and fire-cracked steel does.
    http://forum.gon.com/showthread.php?t=449357
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    SoreShoulderSoreShoulder Member Posts: 3,138 ✭✭✭
    edited November -1
    quote:Originally posted by JustC...I can't see how even a long shot string of overbore magnums could create enough temperature, throughout the barrel's thickness, ...
    Why would it have to anneal the whole barrel in order to wear out the throat?

    The barrel does get hot, so air or no air, there's something behind the surface keeping it warm enough, possibly long enough, for just the very top layer to soften up, then due to the large thermal reservoir of the barrel it may cool slow enough.

    Reading your posts, a person would come away thinking that ALL worn barrels look like a dry lake bed.
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    JustCJustC Member Posts: 16,056 ✭✭✭
    edited November -1
    never saw a worn barrel that wasn't fire-cracked. Unless someone with ridiculous cleaning practices wore the muzzle/crown area or beat the throat to death due to no muzzle/bore guide use.

    every "worn" barrel I have ever seen is from being shot-out at the throat, which by definition, means they are always fire-cracked. The rule of thumb is that 40lbs of poweder, burns a barrel out (or to be correct, erodes enough of the rifling lands away, starting at the throat and moving forward, to degrade accuracy) Lets say a 308 using 50grs of powder is the test rifle, which obviously would get 140rnds out of a pound of powder, and therefore would be "worn" out at 5600rnds. IMHO, if you were softening that steel to any real degree during each firing, I don't see how the rifling would last 5600rnds. However, as the distance from the case mouth is increased, the erosion becomes less and less as the plasma has become less dense and has become more of a fire as it extends down the bore. The rifling at 5+ inches from the case mouth, is usually almost like new, with respect to it's height, with some wear at the corners where the bullets engrave their jackets. That alone proves that the vast majority of erosion, is caused by exposure to the plasma that exits the case mouth, but only last tiny fractions of a second, thus the amount of firings needed to erode the throat/rifling. This is not an ar15 or ak etc that is simply run hot at the range while the owner gets the feeling of dumping 30rnd mags into a target 25yds away, of course.

    99+% of hunters, will never wear a barrel enough to even notice a change in the throat area. They simply don't shoot them enough times, or run them hot enough to burn them. Most rifles, even a pre-64 Winchester, have only been fired a few hundred times in their life. This can be proven by running a bore scope in the barrels of trade in guns at the gun store, a practice that most owners employ, since they don't want to have to eat the cost of a rifle they took on trade. have taken bore-scopes to the store to inspect the throats of rifles I was interested in. If the shop owner didn't like it, then I would have to question why.

    that's my take on barrel "wear" (erosion) YMMV
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    Tailgunner1954Tailgunner1954 Member Posts: 7,734 ✭✭
    edited November -1
    Running my "standard" hunting load (150gr NBT, 61.5gr Rl-19 in a Rem 30-06 case), I put 4700 rounds through a Shilen barrel before the accuracy went south. Setting the barrel back 1 thread was not enough to completely clean up the "gater skin" in the throat, but it was enough to allow another 2500 rounds before the accuracy again fell below acceptable levels (IE: greater than 1.5 MOA average, or double it's "like new" average group).
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    SoreShoulderSoreShoulder Member Posts: 3,138 ✭✭✭
    edited November -1
    There are bores where the rifling has receded without a lot of alligatoring.

    On those, if it was all gas erosion, you would think the grooves would recede almost as much as the lands, but it doesn't seem to be completely the case.
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    sandwarriorsandwarrior Member Posts: 5,453 ✭✭✭
    edited November -1
    It's gas/erosion. Think of how bad a barrel gets from the throat to up one inch forward of that. Also think, in comparison, of how long the bullet stays in the barrel without doing hardly any damage.

    Most of the throat is worn away. While a couple inches down the barrel all the way to the muzzle is near perfect. A bullet sliding 20-25+ inches down the barrel not causing much if any wear, losing significantly less than the throat, which absorbs 90+% of the hottest gasses.
    That tells you right there, high pressure gasses cause the most erosion.

    Added:

    My age old analogy applies directly to this topic as well.

    "Think of a round going off in the barrel like tuning a blowtorch for cutting. When you have O2 and acetylene just burning you see a long mild blue tip. Turn the mix just right and you see a sharp bright blue tip. That's where the metal gets cut."

    Soreshoulder brings up a good point. But, as nemesis said it reinforces not undermines the subject.
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    charliemeyer007charliemeyer007 Member Posts: 6,579 ✭✭✭
    edited November -1
    I think it would be fun to do an OKH approach (light the powder at the base of the bullet) to a .50 BMG Improved running only ball powders.
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    machine gun moranmachine gun moran Member Posts: 5,198
    edited November -1
    Throat erosion became an immediate problem when cartridges started transitioning from black powder to smokeless. When the Brits changed to Cordite in their .303's, their barrel throats started summarily disappearing. They experimented with different rifling forms, until they came up with the one that would give the longest service life in the throat (five approximately equal-width lands and grooves).
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    MIKE WISKEYMIKE WISKEY Member, Moderator Posts: 9,988 ******
    edited November -1
    just to note; most rifle barrels are 'stress releaved' read annealed, all quality barrels are dead soft steel (no heat treating to harden them). The one (1) barrel that I've worked on that had any hardening at all was a Jap. browning .22 auto that had the feed ramp hardened.
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    SoreShoulderSoreShoulder Member Posts: 3,138 ✭✭✭
    edited November -1
    quote:Originally posted by MIKE WISKEY
    just to note; most rifle barrels are 'stress releaved' read annealed, all quality barrels are dead soft steel (no heat treating to harden them). The one (1) barrel that I've worked on that had any hardening at all was a Jap. browning .22 auto that had the feed ramp hardened.
    Stress relieving is not annealing.

    Not all barrels are even stress relieved because if they were then why can't you machine some barrels without affecting the internal contour? Barrels that are supplied as blanks are stress relieved so they could be machined without fear of ruining the bore but not all barrels are.
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    SoreShoulderSoreShoulder Member Posts: 3,138 ✭✭✭
    edited November -1
    quote:Originally posted by JustC
    never saw a worn barrel that wasn't fire-cracked. Fire alone won't make it crack. It will erode and soften it.
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    SoreShoulderSoreShoulder Member Posts: 3,138 ✭✭✭
    edited November -1
    quote:Originally posted by MIKE WISKEY
    just to note; most rifle barrels are 'stress releaved' read annealed, all quality barrels are dead soft steel (no heat treating to harden them). They are hardened and then tempered to remove much but not all the hardness. I think they tempered to a dark blue oxide in the days of temepring by eye.

    The strength of AISI 4340 steel is only 60,000 psi when dead soft. If it were under firing pressure the stress inside would be hydrostatic so it wouldn't necessarily fail even under an overload of 70,000 psi but then the bullet would hit the rifling and the root of the land would fail. It's gotta be hardened or guns couldn't run at 65,000 psi.
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