Long throat & barrel erosion

I was discussing the erosion of the barrel on my Axis with a guy and he has a theory that a barrel with a long throat would erode faster than a shorter one. I don't know if this is true but the Axis did erode at a rate nearly 9 times the rate of the other 223.

I also have a fairly good estimate of how many rounds was through it. I didn't start shooting, at least as much as I do now, until fairly recently. I looked at all of the bullets I bought from various suppliers and the total number of bullets is right at 3200. The 3200 would be divided up among three 22 caliber rifles and the Axis was the last one I bought. There is no way it could have over 1500 rounds through it. It has never used factory ammo, everything was handloaded at between min and max load using Hodgdon data. Probably 3/4ths of the time I used CFE 223, probably 20% of the time 3031 and the remainder something else.

Any opinions on the long throat erosion idea?

I don't think it's the long throat that is the issue- but the relationship between the throat and bullet. If the bullet has a long way to travel before it seals up the barrel then it is going to let more hot gas around it and that will cause more erosion. I have some barrels with very long throats- but they shoot heavy for caliber bullets- and they don't seem to wear fast.

Also- boat tail bullets cause more erosion than flat base because of how they funnel the gas to the sides.... as well as bullet construction and how easily they bump up and seal the bore..... so it has a lot more variables than just round count.

What he said would be a theory for me as well.

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That is interesting that boat tail bullets are harder on barrels. A lot to think about. I have also heard heavier bullets are harder on barrels. You would think with more powder on the lighter bullets they would be worse but some say the gases have more time to do their damage since the bullet moves slower.

The powder type and amounts are the main culprit of erosion. Certain powders just wear out a barrel faster than others. Particularly IMR powders.

Heavier bullets can be harder on the barrels, if the jump is the same as a lighter bullet.

Takes longer to get moving, so longer to seal the barrel.

Yep, powder types and powder charges matter as well.

I put a ton of rounds through my .223 barrel, most of them 77gn and large charges of Varget, with a little jump. One of these days I need to measure the throat to see how much it actually changed. I never changed how far out I seat the bullets in over 4000 rounds.

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Bullets have little or nothing to do with barrel erosion. Heat is what kills barrels.

...and poor metallurgy.

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Originally Posted by sharpshooter

Bullets have little or nothing to do with barrel erosion. Heat is what kills barrels.

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I'm interested in the research that you have done to be able to rule bullet shape/construction out of it? Heat is a huge part of it..... where that heat is focused is also huge. It is the reason that a 6mm Rem will have better barrel life than a 243 win if you shoot the same bullet at the same pressure-- because the 243 neck/shoulder focus the gas to the sides as it comes out of the case.... and the 6mm rem with the shoulder and longer neck focuses the gasses and unburnt powder down the bore. Why is the 243 a notorious barrel burner when cartridges that have more powder capacity and speed have better barrel life? Because of where it focuses the destructive heat.... and boat tailed bullets by their design also work as a funnel to direct the gasses to the side of the barrel instead of down the bore.

I'm always interested in learning new things- and lots of shooting lore has been debunked....

Well, Many 243 loads are using the lighter bullets at laser beam velocity. 3500, 3600, even 3900fps+ from factory loaded 243Win. The 6mm Remington was designed for the heavy(at the time) projectiles. Can’t really find 6mmRem with light bullets & loaded to insane velocity. It’s those light projectile loads at high velocity roasting barrels. It’s a common Overbore situation. The 243Win loads using 100gr pills at 2950fps are not responsible for the it being labeled a Barrel Burner. Feed your 6mmRem a steady diet of 65gr V-max at 3800, or 3900fps and see how long the barrel lasts. ;)

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Originally Posted by Dave Hoback

Well, Many 243 loads are using the lighter bullets at laser beam velocity. 3500, 3600, even 3900fps+ from factory loaded 243Win. The 6mm Remington was designed for the heavy(at the time) projectiles. Can’t really find 6mmRem with light bullets & loaded to insane velocity. It’s those light projectile loads at high velocity roasting barrels. It’s a common Overbore situation. The 243Win loads using 100gr pills at 2950fps are not responsible for the it being labeled a Barrel Burner. Feed your 6mmRem a steady diet of 65gr V-max at 3800, or 3900fps and see how long the barrel lasts. ;)

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Backwards....the 6mm (244) was designed for light bullets and lost the popularity contest to the 243 because it couldn't do the dual purpose role (varmint and deer) as well as the 243. The 244 (6mm) had a 1-12 and the 243 had a 1-10. Looking at factory loads doesn't do much good because the 6mm Rem just isn't popular enough to have the ammo support that the 243 does. But hand load them with the exact same bullet and the 243 still has shorter barrel life (in equal barrels).

Also- lots of discussion about bullet weight and barrel life..... my view is that heavy bullets are actually harder on barrels than light bullets. The light bullets start and travel faster so they have less dwell time in the barrel than heavy bullets-- even though light bullets have more powder behind them and more velocity.

Well, ok.. go try to find a factory load of 6mm Rem. using light bullets. And then do the same for 243 Win. So yeah, I look at things as they ARE. Not what they “might” have been, or thought to be 50 years ago.

Overbore and speed(which typically go hand in hand) are the enemy. And as Fred point out, Heat. More powder, smaller bullet, more speed all equal more heat. Case shape and even neck length have no conclusive evidence backing up their argument. It’s all Anecdotal. Sorry, I just really hate anecdotal evidence used to prove something. And so many do it.

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Originally Posted by Dave Hoback

Well, ok.. go try to find a factory load of 6mm Rem. using light bullets. And then do the same for 243 Win. So yeah, I look at things as they ARE. Not what they “might” have been, or thought to be 50 years ago.

Overbore and speed(which typically go hand in hand) are the enemy. And as Fred point out, Heat. More powder, smaller bullet, more speed all equal more heat. Case shape and even neck length have no conclusive evidence backing up their argument. It’s all Anecdotal. Sorry, I just really hate anecdotal evidence used to prove something. And so many do it.

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Well- I would personally consider looking at what factory ammo is available and then forming an opinion off that as anecdotal evidence also. What does it matter what is factory available- and (not sure) but didn't I read that you have guns that have never fired a factory round? Does case design only come into play in factory loads or would it apply to hand loading as well? Overbore is overbore- it doesn't matter if you are pushing a 55 grain bullet down the barrel or a 80.... it's still overbore-- so not sure how it's the speed that makes the difference. Mechanical wear- from the bullet- is a small % of the total wear-- heat and where it is focused.... like a cutting torch. And to claim that "case shape and neck length have no conclusive evidence" is 100% wrong.

Please don’t add things to what I’m saying my friend. I never said anything about the bullet creating mechanical wear, and to infer that I did is simply disingenuous.;)

No, my mention of overbore and a smaller bullet is those are the criteria needed for a greater powder charge which all translates to more speed. More speed equates to more HEAT..period. If you don’t understand that greater speed brings greater heat, I’m sorry. That’s physics. These factors bring us once again to what Fred pointed out. Heat is the issue. I was simply addressing the avenue by which the heat is established. Also, no.. what I said about case shape & neck length is not 100% wrong. I’m actually 100% correct in saying it’s a heavily debated topic. I can post article after article, various opinion pieces and threads in different forums through the years with peoples “findings”, if you like. I even know where YOU got what you said about case shape, and where the heat is directed.. It came from a so called article by Speedy Gonzales.. apparently with drawings & graphs, whatever… I don’t know, never have seen the article. But I DID read about it in a thread in Accurate Shooter, from 2012. That opinion even focused on 243 Win & 6mm Rem, just as you did.(what a coincidence,;)) Either way, it’s an opinion given by One Man, read & believed by others & regurgitated for still more to read & even take as their own findings years later…. Anyway, my point was it’s a debated topic with Case Shape/neck length/shoulder angle. I never said they have nothing to do with overall function. I simply pointed out there is discourse in those characteristics contributing such a great deal to erosion.

If you would like to learn more about a projectile’s speed & how heat comes about, research the RailGun. The most powerful examples can propel projectiles at over Mach 7 ( 8,200FPS actually!). The gun literally rips itself apart! On every shot, internal pieces of the barrel are ripped off & spit out! Simply because the projectile is traveling so fast & developing so much heat in such a short amount of time. Super interesting reading & watching!
But that’s all I’ll say. :tea:

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Originally Posted by Robinhood

...and poor metallurgy.

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Could it be possible that my Axis for one reason or another had defective material in the barrel? I don't know as much as I would like about barrels are made but I believe the regular ones are made of 4140. I don't know if the steel comes to them with a hardening process or not but would think it would if it does go through a heat treatment process. I would think if they did it after the machining and rifling the heat would distort the barrel. I had a 243 Savage that also wore out the barrel but the 243 is much harder on barrels and I would say it probably lasted about what one would expect for the caliber so I believe Savage, on average, have decent barrels. My other 223, which fired roughly the same amount and was treated the same with regard to cleaning, bullets and powder wore far less. The Axis wore .070" compared to .008" for the other rifle. Something doesn't make sense that there could be that much difference.

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Originally Posted by Mr.Snerdly

Could it be possible that my Axis for one reason or another had defective material in the barrel? I don't know as much as I would like about barrels are made but I believe the regular ones are made of 4140. I don't know if the steel comes to them with a hardening process or not but would think it would if it does go through a heat treatment process. I would think if they did it after the machining and rifling the heat would distort the barrel. I had a 243 Savage that also wore out the barrel but the 243 is much harder on barrels and I would say it probably lasted about what one would expect for the caliber so I believe Savage, on average, have decent barrels. My other 223, which fired roughly the same amount and was treated the same with regard to cleaning, bullets and powder wore far less. The Axis wore .070" compared to .008" for the other rifle. Something doesn't make sense that there could be that much difference.

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Absolutely there could be an issue with the barrel from the factory. It’s. Always a possibility.


Savage just specifies Carbon Steel for the barrels, however, it likely is 4140. They make the barrels from round Bar-Stock. No, it doesn’t come hardened or anything. They perform every process, drilling, reaming, button rifling & lapping. The barrels aren’t “heat treated” per say, rather they are stress relieved after button rifling process, also called Normalizing. This entails heating to a certain temp below Austenitizing temperature; usually a little over 1,000F, for a period of time. And hour or so.

Here is a video from Savage showing & explaining their processes.
https://www.youtube.com/watch?v=EUkekGATrfQ

You can take the 243 and load it with imr4350 and the 6mm rem with varget. Both with the same bullets at the same speed. Or switch the powders from one to the other. Which ever is running the IMR powder will blast the throat out of the barrel faster than the other. It is not heat that is causing it. Or the angle of the shoulder. It is the powder sand blasting the throat.

Opp! A completely new theory with absolutely no evidence whatsoever! LOL!:stupid: Iv’e heard the theory that Slower burn rate powders wear the Throat faster than quicker burn rate powders. And Iv’e heard it mentioned by a person or two that Ball powders wear slower than stick powders. But this Sand Blasting theory…. It’s a new one. I guess it makes as much sense as the others, haha!

Dave,

Speed and the heat involved with the gas plasma are not directly proportional. There are two parts (actually a couple more lesser parts as well) to this.

The first part of the gas plasma and how it interacts with the throat has to do with how fast the bullet engages the full dia of the grooves. This is the gasses and particles than get around the bullet. FWIW, this is the action that causes most of the copper fouling in the bore. This is also where the theory that a boat tail bullet can be worse than a flat base. I have not seen any proof of that in experimentation.

The gasses behind the bullet after it fills the grooves affect the heating of the throat and are related to the speed of the bullet. They are also related to the powder granules themselves as well, as some others pointed out. You can have a faster bullet with one powder that erodes the throat less than another slower bullet with a more 'abrasive' powder.

FWIW, the heat that damages the throat is the heat level of the plasma and the initial 'jet' effect of the plasma, not the friction component. The friction is the major source of heat on the bullet itself and it gets hotter as it proceeds down the barrel (as it speeds up).

If you want to learn a lot more about this the Army has a series of manuals that deal with guns. Mostly for use with artillery shells, but much of the analysis is pertinent to rifles and sometimes pistols.

US Army Material Command, AMCP 706-150 is the one for internal ballistics. There is another for how gun barrels are designed, one for the design of shells, and another for external ballistics. Plus some that deal with explosives and explosive warheads. I don't have mine anymore so can't give the numbers off the top of my head.

The rail gun has no combustion plasma behind the projectile. It is basically a big electric arc, which is why all the heat and loss of rail material. The projectile itself does not touch the rails. There is a carrier (early designs they called it a shoe, don't know what they call it now) that the projectile fits in. The carrier is the conductor for the rails. Early designs were a problem because of all the arcing. Basically they were a throw away single shot. The advancements over the past 45 years has been in perfecting the electric power switching and how the 'shoe' interacts with the rails. Yes, the Army fired it's first rail gun back in the 1970's (maybe even before since it came out of a classified program).

Dave
I thought you were talking about mechanical wear because you keep bringing up "speed".... not pressure. Yes - you need pressure to get more speed, but you load to the same pressure with a light fast bullet as you do with a heavy slower one- so speed isn't the issue. I've burned out many 22-250 barrels and they have lasted longer with the 40 grain bullets going supper fast than they have with the 88-90 grain bullets.

I picked 243 and 6mm because I have them each (and burned out barrels in each so that it wouldn't be necessary to just regurgitate others info:cool:) It was an article that got me to experiment with them- talking about a guy that used 243 for matches and loaded his ammo to different lengths because by the latter stages of the match his throat would be worn so much-- not sure if that was Gonzales or not- either way I tested it- and loaded with same bullet- same powder at same velocity the 243 was much harder on the throat.

Also- pertaining to boat tail bullets (primarily what I use) they still direct hot gasses to the barrel and let hot cutting gases past the bullet before they seal the bore. Have you ever seen those high speed pics of different bullets leaving the barrel? The BT bullet has considerably more gasses in front of it than a Flat base- and that can't be good for the throat.

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Originally Posted by Dave Hoback

Opp! A completely new theory with absolutely no evidence whatsoever! LOL!:stupid: Iv’e heard the theory that Slower burn rate powders wear the Throat faster than quicker burn rate powders. And Iv’e heard it mentioned by a person or two that Ball powders wear slower than stick powders. But this Sand Blasting theory…. It’s a new one. I guess it makes as much sense as the others, haha!

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Tell that to Ed Harris. It is a thing. I think Hornady even mentions it in their books

https://www.hensleygibbs.com/edharri...dharrisbio.htm

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Originally Posted by tomme boy

Tell that to Ed Harris. It is a thing. I think Hornady even mentions it in their books

https://www.hensleygibbs.com/edharri...dharrisbio.htm

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Mr "Ed's Red" himself and avid cast shooter. :thumb:

And frequently on the Cast Boolits forum. A really nice guy as well.