Burning Powder

[4Mesh]

So far, I see no scientific data whatsoever. I see talk about powders of 60 years ago causing chemical wear. On opinion from someone at Sierra (no data, and certainly not what I'd call authoritative opinion), suggesting pressure does this, but nowhere saying through what medium. Then another link to some guys personal site that begins with

A (Very) Short Course in Internal Ballistics

Internal ballistic, or the science of what goes on inside of the gun, is a very complicated topic. This page is not designed to give you a degree in the field but rather to provide some background data to help you understand the subject.

Again, probably more data collected from someone elses flawed works.

Car engines seem to work for a lot of firings. What happened to the heat and pressure there? Valves don't wear out very quick for all the punishment they take do they? So, how many Millions, and millions of times do they fire in a lifetime? What's the difference? Oil and dirt...

Who came up with these percentages of energy and from what data? I didn't see someone show where those numbers came from. Did I miss that? So far, those I saw I didn't agree with. So...

So answer Matts question above. DKHunt. Why does the lower half of a barrel wear more than the top? You've come up with such statements as to imply that the gas in front of the bullet cleans the barrel before every shot. As if I say unburnt powder is still whole extrusions or something. (in some cases, it is). But, I'm talking about the dirt left behind and most guns do that.

Rhetoric alright. Go do some testing of your own. Do you own a borescope? Have you ever shot out barrels without rechambering and rotating them? Sounds like not...

I'm still wondering how cases do not wear, but barrels do. Some folks get a lot of firings from cases, without them wearing out. Interesting they're not consumed too.

Hey, I have one for you. I have seen a piece of wax, stuck inside a case that was fired, still sitting in the case afterward. Not melted, not deformed, just a little dirty. Hmmm, all that heat... doesn't even have time to melt wax, but it'll melt stainless steel. But won't hurt brass. Oh, yea, the brass must have conducted the heat away from the wax, I forgot.

 

[goodgrouper]

So far, I see no scientific data whatsoever. I see talk about powders of 60 years ago causing chemical wear. On opinion from someone at Sierra (no data, and certainly not what I'd call authoritative opinion), suggesting pressure does this, but nowhere saying through what medium. Then another link to some guys personal site that begins with Again, probably more data collected from someone elses flawed works.

Car engines seem to work for a lot of firings. What happened to the heat and pressure there? Valves don't wear out very quick for all the punishment they take do they? So, how many Millions, and millions of times do they fire in a lifetime? What's the difference? Oil and dirt...

Who came up with these percentages of energy and from what data? I didn't see someone show where those numbers came from. Did I miss that? So far, those I saw I didn't agree with. So...

So answer Matts question above. DKHunt. Why does the lower half of a barrel wear more than the top? You've come up with such statements as to imply that the gas in front of the bullet cleans the barrel before every shot. As if I say unburnt powder is still whole extrusions or something. (in some cases, it is). But, I'm talking about the dirt left behind and most guns do that.

Rhetoric alright. Go do some testing of your own. Do you own a borescope? Have you ever shot out barrels without rechambering and rotating them? Sounds like not...

I'm still wondering how cases do not wear, but barrels do. Some folks get a lot of firings from cases, without them wearing out. Interesting they're not consumed too.

Hey, I have one for you. I have seen a piece of wax, stuck inside a case that was fired, still sitting in the case afterward. Not melted, not deformed, just a little dirty. Hmmm, all that heat... doesn't even have time to melt wax, but it'll melt stainless steel. But won't hurt brass. Oh, yea, the brass must have conducted the heat away from the wax, I forgot.

You're starting to sound like the liberal media when asked to provide facts of their own, or name sources. They just defer, defer, defer..................

Again, quit going over what I said (or apparently what you think I said) and give us some proof to back up your beliefs. No gut feelings, no cars, no mufflers, no bs. Just give us one bloody scientific shred of evidence that proves that "dirt" is the reason why barrels wear out and increased pressure extends barrel life! PLEASSSSSSSSSSSSSSSSSSSSE!

 

[4Mesh]

So refer me to the post here with "Science". You provide your opinion that you cannot back up with anything other than to say someone else said it, somewhere. Some guy from Sierra vaguely refers to this, and so it makes your unsubstantiated claims true. All the things I say have been observed by myriads of shooters and/or gunsmiths. Many of whom have spent lifetimes at these games (professional by any measure). You are just like a politician, burying your head in the sand when certain conditions do not satisfy your solution to the problem. Your "Science" refers to finding a solution, then attempting to make conditions to prove that solution to fit. Anything inexplicable comes up, just tell everyone they don't understand real science as verified by any number of quacks with websites.

I don't know of too many "competitive" (meaning, people who win regularly) shooters who have issues with throat wear any more. In any caliber. Yea, barrels eventually wear out, but, throat movement is basically a thing of the past. Well, for those a little smarter than you anyway. So, you go ahead and claim pressure and heat does all this, and I will continue to say it doesn't happen in my rifles, or in those of many other shooters, and has not for some years. Think what you wish.

 

[goodgrouper]

Yet another deferment............
I guess that's all we're gonna get. Bummer.

 

[goodgrouper]

Andy, Al, Keith, Kevin, you guys getting any of this? Apparently we're all in Neverneverland. Funny, I thought I remembered Tinker Bell being cuter............

 

[mks]

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...

Oops, I didn't say that quite clearly. 25% of the pressure (15 kpsi) is what is left after all the losses, and gets converted to bullet velocity. The change is bore friction for a 0.002" longer bearing length is 7.2 psi, so the net pressure drops from 15,000 psi to 14992.8 psi, a 0.05% decrease.

The air column in a 30" 0.308 barrel weighs 0.63 grains and changes about 3% for every 10 degrees C temperature change.

I've seen some tests on coated and uncoated M80 and Barnes solid copper bullets in a M240 barrel. Forces ranged from 1000 to 5000 N = 225 to 1125 lb. My guess is the Berger would be a bit more than the M80, but less than the Barnes. Depends on the barrel, too, though.

Cheers,
Keith

 

[HovisKM]

Goodgrouper,

I've gave up on this. He's not even in the same universe.

The funny thing is, no one has said that friction and fouled barrel doesn't cause wear (he keeps saying we are) but that it is one of the least causing factors that cause barrel wear and accuracy degration.

Also, he has never explained why firecracking takes place in a barrel, it sure isn't friction that causes it and it's apparent that he doesn't understand what he is looking at with the borescope. If you watch the firecracking at entervals, you can obviously tell the erosion is coming from firecracking.

As far as the lower part of the lands wearing quicker, yes it does but it again is very minor. I have a barrel with over 6000 high pressure rounds down it. Just shot two three shot groups last night to check a load, one was a zero and the other a low one. The barrel looks like crap with a bore scope, pieces of lands missing, throat almost gone, pits, etc. BUT the bullet still contact the lands evenly all around it's circumferance. If you look at the bore with a scope, you would never think so. I personally have never had a barrel that stopped shooting where a land wasn't contacting the bullet. I go through about six barrels a year on average for the last ten years in just 6PPC.

I also had a chance at last years East-West shoot to watch a barrel go from shooting in the low ones to upper two's in 150 rounds. I checked the barrel with a borescope after every group for a whole day and it was amazing to watch it go. It sure wasn't friction that did it.

I almost downloaded this thread and sent it to a couple of my friends at the Joint Forces Special Weapons department but they would probably laugh so hard they wouldn't get any work done for a couple of days.

AGAIN, friction and fouling does cause wear in the bore, but do to the way we take care of BR barrels and shoot them, and it being such a minor factor, we just don't worry about it because all the other factors wear the barrel out long before friction will.

Hovis

 

[mike in co]

so any guess why he is on my ignore list ???

 

[4Mesh]

You're starting to sound like the liberal media when asked to provide facts of their own, or name sources. They just defer, defer, defer..................

Again, quit going over what I said (or apparently what you think I said) and give us some proof to back up your beliefs. No gut feelings, no cars, no mufflers, no bs. Just give us one bloody scientific shred of evidence that proves that "dirt" is the reason why barrels wear out and increased pressure extends barrel life! PLEASSSSSSSSSSSSSSSSSSSSE!

I think YOU are the one who defers. YOU are the one who claims heat and pressure consume the metal. I say it does not. Show scientific proof of why this is true, and don't use examples of texts written about large bore guns on ships or other inapplicable weapons. We're talking about match rifles and small arms here.

This report shows basically that Ablation causes surface degradation, but MECHANICAL wear removes the material. This though is in reference to large guns (guns, as in artillery or ship pieces) and they are looking for wear of .040".
http://science.gov/scigov/link.html.../www.dtic.mil/dtic/tr/fulltext/u2/a085720.pdf

Finding reference to small arms is pretty difficult, or near impossible. Which is why I ask you to provide some facts to back up your claims. But all you do is point me to Sierra bullets site or some other bozo's site, with lots of ambiguity, but no facts. Clearly, someone else told them what to say,so they parrot that.

If I fire a match rifle that has bore dimensions of .300 and .308, by your claims, it should "WEAR" and become .308 and .316. But funny enough, it just becomes .308 doesn't it? The rest of the barrel doesn't wear till the rifling is gone. Can the pressure not reach into those grooves? Why is your pressure so selective Mr Scientist?

Why is it that only the part that touches the bullet is what "pressure and heat" burn away? Why don't the grooves wear away too? Why doesn't the case wear away too?

Come on Mr Science? Show me a QUANTIFICATION of heat and pressure eating metal and at what rate? I want to see 1 seconds worth of wear shown to be 50 or 100 thousands like we see in rifles.

Edit again...

PS, read that report above and take note that they find NO evidence that any metal ever melts. Not through modeling nor in actual analysis of used barrels. So their info at least shoots that theory in the ass too.

 

[goodgrouper]

Goodgrouper,

I've gave up on this. He's not even in the same universe.

The funny thing is, no one has said that friction and fouled barrel doesn't cause wear (he keeps saying we are) but that it is one of the least causing factors that cause barrel wear and accuracy degration.

Also, he has never explained why firecracking takes place in a barrel, it sure isn't friction that causes it and it's apparent that he doesn't understand what he is looking at with the borescope. If you watch the firecracking at entervals, you can obviously tell the erosion is coming from firecracking.

As far as the lower part of the lands wearing quicker, yes it does but it again is very minor. I have a barrel with over 6000 high pressure rounds down it. Just shot two three shot groups last night to check a load, one was a zero and the other a low one. The barrel looks like crap with a bore scope, pieces of lands missing, throat almost gone, pits, etc. BUT the bullet still contact the lands evenly all around it's circumferance. If you look at the bore with a scope, you would never think so. I personally have never had a barrel that stopped shooting where a land wasn't contacting the bullet. I go through about six barrels a year on average for the last ten years in just 6PPC.

I also had a chance at last years East-West shoot to watch a barrel go from shooting in the low ones to upper two's in 150 rounds. I checked the barrel with a borescope after every group for a whole day and it was amazing to watch it go. It sure wasn't friction that did it.

I almost downloaded this thread and sent it to a couple of my friends at the Joint Forces Special Weapons department but they would probably laugh so hard they wouldn't get any work done for a couple of days.

AGAIN, friction and fouling does cause wear in the bore, but do to the way we take care of BR barrels and shoot them, and it being such a minor factor, we just don't worry about it because all the other factors wear the barrel out long before friction will.

Hovis

Absolutely. Thanks Kevin. This stuff is basic ballistics 101 and documented all over the place. Just the fact that he's arguing it (like we wrote all the data) boggles the mind.
There ain't no use in trying to educate the guy anymore........he's proven he's irrational as they come.
Btw, you sould send this thread on to your JFSW buddies and brighten their day! I've copied Mesh's comment about increasing pressure to increase barrel life to my desktop notepad so I can have a smile everytime I use that app. It's priceless!

 

[4Mesh]

The funny thing is, no one has said that friction and fouled barrel doesn't cause wear (he keeps saying we are) but that it is one of the least causing factors that cause barrel wear and accuracy degration.

No, you and others say it is insignificant, a few % from various remarks above. I say it is not. I also did not say all wear can be eliminated. I said that increasing pressure so as to burn all propellant causes less residue, and thus less wear. I also said, my throats don't wear or "move". Get all that straight before putting words in my mouth due to the digression of this. The BARREL will wear, the THROAT will not (for all measurable significance).

Also, he has never explained why firecracking takes place in a barrel, it sure isn't friction that causes it and it's apparent that he doesn't understand what he is looking at with the borescope. If you watch the firecracking at entervals, you can obviously tell the erosion is coming from firecracking.

"Firecracking" takes place because of friction causing localized heat in the surface. Expand, contract, you get surface cracks. Who gives a f___ where that comes from, this discussion is about wear in a throat and what causes it. Who is avoiding the subject now? The .002 seconds of "Fire" doesn't impart enough heat in a barrel to do anything. NOTHING. The friction does.

As far as the lower part of the lands wearing quicker, yes it does but it again is very minor.

Minor?? At what % of the wear does it become major?

I have a barrel with over 6000 high pressure rounds down it. Just shot two three shot groups last night to check a load, one was a zero and the other a low one. The barrel looks like crap with a bore scope, pieces of lands missing, throat almost gone, pits, etc. BUT the bullet still contact the lands evenly all around it's circumferance. If you look at the bore with a scope, you would never think so. I personally have never had a barrel that stopped shooting where a land wasn't contacting the bullet. I go through about six barrels a year on average for the last ten years in just 6PPC.

Aw gee, what a revelation! Where there is no contact, there is no wear, therefore, since wear continues to allow contact from a bullet, that proves your theory! Your a joke.

I also had a chance at last years East-West shoot to watch a barrel go from shooting in the low ones to upper two's in 150 rounds. I checked the barrel with a borescope after every group for a whole day and it was amazing to watch it go. It sure wasn't friction that did it.

Hmmm, so why don't all barrels do this? Huh, only this one had heat in it? Wth does this have to do with the discussion anyway? Did you do a study to find out why this barrel wore out in 150 rounds when others wear out in 6000? Ya know, I once had a gun shoot bigger in the afternoon than it did in the morning too. Never crossed my mind that it was worn out. Especially when it came back another day and shot small again. Musta grown back or something.

I almost downloaded this thread and sent it to a couple of my friends at the Joint Forces Special Weapons department but they would probably laugh so hard they wouldn't get any work done for a couple of days.

By all means, please do.

AGAIN, friction and fouling does cause wear in the bore, but do to the way we take care of BR barrels and shoot them, and it being such a minor factor, we just don't worry about it because all the other factors wear the barrel out long before friction will.

You contend that hot gasses and pressure wear out the barrel for all significant measure. I contend that residue and resulting friction do it, for all significant measure. GG says this is "Documented all over the web". But, doesn't look very documented to me. And I have searched the web a time or two.

You guys twist things to where it's laughable. I bet if we had a discussion about Lead Laps, you'd contend that a lead lap will not lap a barrel. Yup, right, but stick some abrasive in there and guess what it does now.

 

[mks]

This report shows basically that Ablation causes surface degradation, but MECHANICAL wear removes the material. This though is in reference to large guns (guns, as in artillery or ship pieces) and they are looking for wear of .040".
http://science.gov/scigov/link.html.../www.dtic.mil/dtic/tr/fulltext/u2/a085720.pdf

PS, read that report above and take note that they find NO evidence that any metal ever melts. Not through modeling nor in actual analysis of used barrels. So their info at least shoots that theory in the ass too.

This is an interesting report. It uses a shock tube gun to cause erosion in test samples that are not in contact with anything other than pure gas mixtures. No bullet friction, no gunpowder and no "dirt." They found erosion due to melting of the steel and due to oxidation of the steel, with the material carried away by gas shear stresses in both cases. They also hypothesized that iron carbides may be formed that have a lower melting temperature, allowing erosion at temperatures lower than the melting point of pure steel.

PS. From this report, one could extrapolate that a possible reason that brass is eroded less than steel is that it resists oxidation.

Cheers,
Keith

 

[4Mesh]

PS. From this report, one could extrapolate that a possible reason that brass is eroded less than steel is that it resists oxidation.

You mean sorta like Stainless?

Their testing was with long durations, not .002 sec.

Cheers,
Phil.

 

[mwezell]

You mean sorta like Stainless?

Their testing was with long durations, not .002 sec.

Cheers,
Phil.

I'm not here to argue with anyone.
There are two points that raise question to me specifically.
One is that you seem to contend that over the life of a barrel(1-2 seconds) that friction is what makes the barrel heat up and does the damage to the barrel and that the heat from the burning of the powder is negligible.
Am I understanding you right?
The other thing is, if the heat is from friction, how do/would you explain heat in the barrel while fireforming w/o a bullet?
Thanks.

 

[4Mesh]

I'm not here to argue with anyone.
There are two points that raise question to me specifically.
One is that you seem to contend that over the life of a barrel(1-2 seconds) that friction is what makes the barrel heat up and does the damage to the barrel and that the heat from the burning of the powder is negligible.
Am I understanding you right?
The other thing is, if the heat is from friction, how do/would you explain heat in the barrel while fireforming w/o a bullet?
Thanks.

1. Yes you are understanding my assertions correctly.
2. Because when you fireform with no bullet, much of the powder is not burnt in the "pressure" phase. That powder lays there and finishes burning in the barrel. As you've probably seen, pieces of powder lay in the barrel afterward, or fall back in the case if you hold it vertically. It's not a clean burn, all done, in one bang. There, you're dealing with heat over comparatively 300x? 500x? the time? There is also friction, but it is probably marginal (insignificant).

Interesting that nobody wants to explain why the tops of lands burn and wear, but the grooves do not.

 

[HovisKM]

4Mesh,

YOUR the only one everyone is laughing at.

Well, I guess I must throw away the gas torch and just rub some copper/lead with some inbedded fouling on what I want to cut....

Hovis

 

[mike in co]

on the top of the page on the right hand side,
click on "settings"
on the settings page, about half way down on the left side
click on "edit ignore list"
on the ignore list page,
type "4mesh" in the open box.
click "okay"
and the problem disappears...

mike in co

 

[mks]

You mean sorta like Stainless?

Their testing was with long durations, not .002 sec.

Cheers,
Phil.

They used 4340, but my guess is that brass is less oxidizable than 316 stainless. Maybe a metallurgist can chime in.

Yes, a little longer - a range of projectile velocities from 600 - 2250 fps.

The main point is that they documented erosion with nothing affecting the test samples other than temperature and gas flow. Seems like this disproves your theory that friction is the main cause of wear. Do you now want to discredit the report that you offered to support your case?

Keith

The lands, particularly the edges, have higher heat transfer and are exposed to higher gas shear stress than the grooves.

 

[alinwa]

A'gain, the answer is conduction....

 

[4Mesh]

They used 4340, but my guess is that brass is less oxidizable than 316 stainless. Maybe a metallurgist can chime in.

Yes, a little longer - a range of projectile velocities from 600 - 2250 fps.

The main point is that they documented erosion with nothing affecting the test samples other than temperature and gas flow. Seems like this disproves your theory that friction is the main cause of wear. Do you now want to discredit the report that you offered to support your case?

Keith

The lands, particularly the edges, have higher heat transfer and are exposed to higher gas shear stress than the grooves.

That's quite a reach to go from "They found erosion" to "It's the biggest culprit". They also mention that without mechanical wear, there isn't hardly any. Let's put those two together. I never said it did 0, only that it isn't the primary cause. And I still stand by that.

Al
Please elaborate. Metals don't conduct all that differently when you're talking about short terms. One metals ability to carry heat away will make no measurable difference when you're talking about milliseconds. How is conduction even an issue?