Did I burn up my 6GT at a match?

I could see with a heavier bullet with longer bearing surface increasing pressure dwell time as it accelerates slower down the bore and that increasing throat wear without mechanical friction wear happening further down the barrel.
I know nothing about this and don't have the intellectual horsepower to make any scientific assumptions. I'm just a redneck who likes to shoot.
 
Update:
I ran a few of the 115 Dtacs through her tonight and 1 of 6 blew up in transit to the 100 yard target...
Time for the bore scope, then possibly a trip back to Proof for a forensic analysis.
 
Question for those advocating that friction between the bullet jacket and bore has a major effect on barrel wear:

100% of shot out barrels have the most damage immediately in front of the chamber. The lead and throat have the most severe damage and that damage decreases with distance away from the chamber. Even the most severely shot out barrels have almost pristine bore condition for roughly 2/3 to 1/2 the length as measured from the muzzle back. This pattern exists in barrels that were shot out with 100% heavy bullets (competition shooters) as well as those shot out with 100% light bullets (coyote and PD hunters).

This is exactly why many discuss and elect to "set a barrel back". I am not a fan of that approach at all but it does acknowledge that the only damage is immediately in front of the chamber.

If jacket friction was a major contributor to barrel wear, why does that wear hardly exist as you approach the muzzle?
Wouldn't heat from friction increase as the speed differential of the two surfaces increase? Wouldn't heat from friction be greater toward the muzzle compared to close to the chamber?

Thoughts to the contrary?
Terry I agree. If it wasn't for the contour of some barrels you can cut the breech end off and set the barrel back and get more use out of the barrel. A few issues come up with most people. Just cutting off the breech threads and setting the barrel back say .75" to 1" you do get into cleaner rifling but the wear/damage to the barrel is further up than that. So I'm just picking rough numbers here.... if you got 1500 rounds out of that 300wm barrel the first time... your not going to get another 1500 out of the set back. If I had to pick a rough number I'd say 300ish rounds.

Other issues... depending on the contour will it fit/match up in the barrel channel?

And your losing the length of the barrel.

On one of the barrels that I got back from a bullet maker used for accuracy testing 30cal bullets.... you would have to cut off a solid 6" of barrel to get into nice clean rifling. So on a 26" barrel (see the attached pic) you will end up with 20" finish length on the set back. This was a 308win accuracy test barrel. It went 14,560 rounds and held .5moa or better up until that point. I'd say the first solid 1.5" of rifling in front of the chamber is almost completely gone. 1/3 of the barrel life of this barrel got 200+gr weight bullets fired thru it. Other wise it had 175gr bullets shot thru it.

So I did ask the lab guys that were here today (we didn't get to finish the conversation but I'll be seeing them two more times this week) do longer bullets shorten barrel life. The answer was yes it does. Even running it at the same chamber pressure. Again we have to finish talking some more about it.

For rough numbers they have had our barrels go 19k, 22k and the last one gave up the ghost at 27k + rounds (I'm going to call these freaks and out of the ordinary) but these barrels where getting only 150 to 175gr bullets fired thru them. So if the barrel in the picture that got 5k rounds of the really hvy bullets fired thru it and only went 14k vs the others... that does show that the longer heavier bullets do chew up the barrels faster.

1723574476943.jpeg
 
Terry I agree. If it wasn't for the contour of some barrels you can cut the breech end off and set the barrel back and get more use out of the barrel. A few issues come up with most people. Just cutting off the breech threads and setting the barrel back say .75" to 1" you do get into cleaner rifling but the wear/damage to the barrel is further up than that. So I'm just picking rough numbers here.... if you got 1500 rounds out of that 300wm barrel the first time... your not going to get another 1500 out of the set back. If I had to pick a rough number I'd say 300ish rounds.

Other issues... depending on the contour will it fit/match up in the barrel channel?

And your losing the length of the barrel.

On one of the barrels that I got back from a bullet maker used for accuracy testing 30cal bullets.... you would have to cut off a solid 6" of barrel to get into nice clean rifling. So on a 26" barrel (see the attached pic) you will end up with 20" finish length on the set back. This was a 308win accuracy test barrel. It went 14,560 rounds and held .5moa or better up until that point. I'd say the first solid 1.5" of rifling in front of the chamber is almost completely gone. 1/3 of the barrel life of this barrel got 200+gr weight bullets fired thru it. Other wise it had 175gr bullets shot thru it.

So I did ask the lab guys that were here today (we didn't get to finish the conversation but I'll be seeing them two more times this week) do longer bullets shorten barrel life. The answer was yes it does. Even running it at the same chamber pressure. Again we have to finish talking some more about it.

For rough numbers they have had our barrels go 19k, 22k and the last one gave up the ghost at 27k + rounds (I'm going to call these freaks and out of the ordinary) but these barrels where getting only 150 to 175gr bullets fired thru them. So if the barrel in the picture that got 5k rounds of the really hvy bullets fired thru it and only went 14k vs the others... that does show that the longer heavier bullets do chew up the barrels faster.

View attachment 8479093
Good stuff.
Would still love to hear the discussion regarding the main culprit in the erosion I.E. pressure + heat <> repeated material compression/fatigue.

Thank you so much for taking the time to share! That is appreciated.
 
I suspect the increased pressure leads to higher temperatures. If you think about it water boils above 100°C if you increase the pressure above atmospheric. I bet you get a higher flame temperature with the extra pressure caused by the heavier, longer bearing surface bullets.
 
do longer bullets shorten barrel life. The answer was yes it does. Even running it at the same chamber pressure.

I’m sure, as mentioned above somewhere, that length of the bullet is a more minor factor in bore wear. Especially since the percentage of length between a long and regular bullet probably isn’t much (not a reloader).

But a longer sanding block does sand faster.
 
Good stuff.
Would still love to hear the discussion regarding the main culprit in the erosion I.E. pressure + heat <> repeated material compression/fatigue.

Thank you so much for taking the time to share! That is appreciated.
Sometimes I think stress erosion from the barrels expanding and relaxing doesn't help at all and is a contributing factor. Just don't know how to measure it offhand or if it's ever been done.

Then you have the flame temp of the powder. If I remember correctly the flame temp at the throat is 2200 to 4000 F. Depends on the type of powder and what the barrel is chambered in etc... and 2200F is the temperature of lava. Yes it only happens for milliseconds inside the barrel but every time you pull the trigger your lighting off the blow torch. Rate of fire is another big factor along with the heat that kills the barrels.

We did talk about the carbon build up and if they had any numbers on how hard the carbon gets inside the barrels. They said they are looking at doing a carbon vs steel test on hardness. Right now the one guy was just guessing/estimating that the hard carbon build up is 45-70Rc on the hardness scale. If that is accurate.... that's basically twice as hard as the steel normally is.

When someone says I cleaned it down to bare metal! Most don't know what it really takes to clean the barrel down to bare metal and how long it takes to do it. Especially once that barrel has rounds on it.

Go back to that pic of the barrel at 14k rounds. That barrel was getting cleaned every 100-150 rounds fired and it's only in 308win. It really doesn't start getting lighter in color until about 6" from the breech end.
 
Terry, I’ve never seen any hard numbers/data but it’s pretty much agreed on by different ammo/bullet makers I’ve talked to that in a given caliber a longer bullet / longer bearing surface will also effect/shorten barrel life.

So like in a 30cal…. A 150gr match bullet vs a 190gr match bullet the 190 is going to be harder on the barrel. A bullet maker/lab guys will be at the shop on Tuesday. I’ll bring the question up and see if they can shed any light on it.

Obermeyer years ago said that was a true thing as well. I remember him saying when breaking in a barrel to use the longest / heaviest bullet you can shoot at a moderate load/pressure/velocity to break in the barrel.

It might have to do with a combination of things…. Type of bullet, type of powder etc… more than just the bullet. Friction, heat?

Later, Frank

Hypothetically speaking, since the lighter bullet spends less time accelerating down the bore (usually with a few grains more of powder), and the heavier bullet spends more time, could the cause be a combination of slower acceleration, high pressure and more burn time with the heavy?

One could say lighter loads spend more time in the barrel, but the powder charges and total/peak pressure curve is also much easier on the barrel as evidenced by comparing 50gr loads from 22 Hornet, 222, 223 and 22-250.


I have a bunch of thoughts on this issue, but typing it out on my illiterate phone sucks sweaty donkey balls.
 
I suspect the increased pressure leads to higher temperatures. If you think about it water boils above 100°C if you increase the pressure above atmospheric. I bet you get a higher flame temperature with the extra pressure caused by the heavier, longer bearing surface bullets.
I do know without increasing velocity that if the pressure keeps going up that it generates more heat. How that translates into more barrel wear I don't know offhand.

So when a guy is loading a given cartridge and hits a wall at say 2850fps and he keeps adding powder to try and get to say 2900fps but the next powder charge that is an extra .5gr of powder but only sees a velocity increase of say 10fps.... your generating more heat with out any real gain in velocity. Then he thinks adding another .5gr powder will give him more but again he doesn't see it. All of this is happening but heat and pressure are going up.

In my 7/6.5PRC testing when I went from 57.0 to 57.5gr of N555 my velocity only increased 4fps on my personal gun. So I dropped all my loads to 57.0. The extra .5gr of powder isn't giving me anything and I'm already at max pressure to begin with which is 65k. The test barrel confirmed the same thing. .5gr of powder and you only got 3fps gain with one bullet and like 20fps with a different bullet but pressures jumped like 300-700psi and again depending on which bullet it was.
 
We keep talking about really big bullets, but I wonder if the same is true if applied to say a 223 between say a 55 grain at 2900 and an 85.5 at 2900. would the same math hold up?
 
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We keep talking about really big bullets, but I wonder if the same is true if applied to say a 223 between say a 55 grain at 2900 and an 85.5 at 2900. would the same math hold up?
I say yes... it applies to all calibers. Shoot a 140gr 7mm bullet and then switch to a 180 or 190gr 7mm bullet. Same thing happens.
 
We keep talking about really big bullets, but I wonder if the same is true if applied to say a 223 between say a 55 grain at 2900 and an 85.5 at 2900. would the same math hold up?

Push two identical cars on a flat surface.
They will feel relatively the same.
Now, take one and lower the tire pressure (increase bearing surface) and add 500 pounds.
Now try and move it.
It takes a much harder initial push to get the second car moving.
It's the same with projectiles.

The chamber pressure knee (the peak of the push) in a standard load peaks at let's say 020ms.
When you increase the weight and the bearing surface that knee now shows up at 015ms.
What does that mean?
It means more powder is burned, more pressure is attained and more heat is created in a shorter span of time and space.

That's the same as the harder push to get the heavier car with low tires moving.

It equals more wear to the leade and throat area...
 
In my 7/6.5PRC testing when I went from 57.0 to 57.5gr of N555 my velocity only increased 4fps on my personal gun. So I dropped all my loads to 57.0. The extra .5gr of powder isn't giving me anything and I'm already at max pressure to begin with which is 65k. The test barrel confirmed the same thing. .5gr of powder and you only got 3fps gain with one bullet and like 20fps with a different bullet but pressures jumped like 300-700psi and again depending on which bullet it was.
Yes, there's obviously a point where the pressure is building faster than the ability of the system to release it. In your case once you hit 57.0gr. If this didn't happen it would be impossible to blow up a gun. Of course case capacity often limits that, unless you use a fast burning powder.

There must be a graph somewhere of the rate of burn of a powder vs bullet weight and pressure. Where you can see the slower powders creating pressure slower, giving the heavier bullets time to get moving and the faster powders hitting pressure at lower velocity.
 
There must be a graph somewhere of the rate of burn of a powder vs bullet weight and pressure. Where you can see the slower powders creating pressure slower, giving the heavier bullets time to get moving and the faster powders hitting pressure at lower velocity.

Such a graph would have to have a good many constraints in place to give any meaningful data.
Something as simple as tagging bullet weight alone as a constant can introduce variables that would skew any comparisons you are trying to make. Two bullets of the same caliber and weight can have drastically different bearing surfaces (Example: 30 cal. 200gr. round nose soft point versus a 200gr VLD) which would not be acceptable in such a technical graph. Staying with one caliber and bullet weight/profile would likely be preferred.

It would be neat to find a light bullet (flat base spitzer ?) with the same bearing surface length as a heavier bullet ( VLD ? ) in the same caliber to run an isolated subset of the test with.

I'm guessing variations in bullet weight will drive more change than length of bearing surface/friction but both would have to be controlled throughout any graphic documenting pressure ^ slaved to burn rate.
 
I do know without increasing velocity that if the pressure keeps going up that it generates more heat. How that translates into more barrel wear I don't know offhand.

So when a guy is loading a given cartridge and hits a wall at say 2850fps and he keeps adding powder to try and get to say 2900fps but the next powder charge that is an extra .5gr of powder but only sees a velocity increase of say 10fps.... your generating more heat with out any real gain in velocity. Then he thinks adding another .5gr powder will give him more but again he doesn't see it. All of this is happening but heat and pressure are going up.

In my 7/6.5PRC testing when I went from 57.0 to 57.5gr of N555 my velocity only increased 4fps on my personal gun. So I dropped all my loads to 57.0. The extra .5gr of powder isn't giving me anything and I'm already at max pressure to begin with which is 65k. The test barrel confirmed the same thing. .5gr of powder and you only got 3fps gain with one bullet and like 20fps with a different bullet but pressures jumped like 300-700psi and again depending on which bullet it was.
So bringing this back to my original post:
Do you believe that shooting heavy for caliber 6mm bullets in a 6 GT match rifle led to bullets blowing up at 900 rounds?
Or do you suppose doubling up on each stage in 90 degree weather could toast the throat with two 10 round strings per stage?

The load I've been running is well below max at 32 grains N150.
My cleaning regiment is C4 with a bronze brush every 100 rounds, followed by CLP.
 
Have you cleaned it since the match all the way down to bare metal? Could be a hard carbon ring. Could be you got a outlier on the barrel life bell curve. Could be there's enough copper in there to do stuff.
I don't believe either of those would be enough to toast a barrel in 900 rounds. I think you have another problem.
 
Since cleaning have you had this same problem when shooting another brand of bullets? I know you said you were still blowing up DTACs, have you run some more Berger through it?
 
So bringing this back to my original post:
Do you believe that shooting heavy for caliber 6mm bullets in a 6 GT match rifle led to bullets blowing up at 900 rounds?
Or do you suppose doubling up on each stage in 90 degree weather could toast the throat with two 10 round strings per stage?

The load I've been running is well below max at 32 grains N150.
My cleaning regiment is C4 with a bronze brush every 100 rounds, followed by CLP.
Offhand the bullets shouldn't be blowing up. What will cause this?

Shooting it the way you did in that temp.. shouldn't have done anything.

You could have compounding issues.... read on.

Is there damage / severe wear to the throat? If the answer is yes... that could be the problem.

What is the bore size? If it's a tight bore 6mm (like .236") that isn't going to help anything and could be compounding the problem. The tighter bore is going to cut into and stress the bullet jacket more... which leads to bullet failures.

How many grooves does the barrel have?

The barrel could have prematurely died as well. If you've cleaned it good and the accuracy isn't there and your blowing up bullets... then something is up with the barrel if you had no issues before/prior to this last shoot you did. Then I would call Proof and send it in for them to look at.

Later, Frank
Bartlein Barrels
 
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So bringing this back to my original post:
Do you believe that shooting heavy for caliber 6mm bullets in a 6 GT match rifle led to bullets blowing up at 900 rounds?
Or do you suppose doubling up on each stage in 90 degree weather could toast the throat with two 10 round strings per stage?

The load I've been running is well below max at 32 grains N150.
My cleaning regiment is C4 with a bronze brush every 100 rounds, followed by CLP.
CLP to me isn't a cleaner. Its a lubricant / protector.

Look in the barrel... do you see any copper build up? If so where is it?

If you see fouling in the bore... copper etc... your not getting it cleaned good enough.
 
Have you cleaned it since the match all the way down to bare metal? Could be a hard carbon ring. Could be you got a outlier on the barrel life bell curve. Could be there's enough copper in there to do stuff.
I don't believe either of those would be enough to toast a barrel in 900 rounds. I think you have another problem.
I soaked the barrel and throat in C4 , then scubbed the heck out of it with a bronze brush like 3 times since the match, tonight I'll get my buddies bore scope to have a look.
Since cleaning have you had this same problem when shooting another brand of bullets? I know you said you were still blowing up DTACs, have you run some more Berger through it?
Yep see above, in addition to the 112s ive only tried the dtacs so far but if it's blowing up 2 different bullets there's obviously a problem. I'll post a description of the borescoping later for sure.
 
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CLP to me isn't a cleaner. Its a lubricant / protector.

Look in the barrel... do you see any copper build up? If so where is it?

If you see fouling in the bore... copper etc... your not getting it cleaned good enough.
I should also mention I ran Butchs Bore shine through, and after analyzing 8 soaked patches there was very little to no copper staining as they dried.
I visual inspection with a light doesn't show any fowling or copper, again the borescope tonight will tell me more on that front.
And just a recap, the 112s were the initial bullets that were blowing up.
I loaded dtacs the other night and they're doing the same thing.
 
Do you have any Non-DTAC bullets you could try? There have been multiple people suggest that DTAC have been doing this. I remember you saying that you had some Bergers. Since the cleaning have they exhibited the same behavior?
 
I should also mention I ran Butchs Bore shine through, and after analyzing 8 soaked patches there was very little to no copper staining as they dried.
I visual inspection with a light doesn't show any fowling or copper, again the borescope tonight will tell me more on that front.
And just a recap, the 112s were the initial bullets that were blowing up.
I loaded dtacs the other night and they're doing the same thing.

I'm going to break from the wisdom of @Frank Green and tell you this is where an abrasive comes in. Based on my experience with 6GT, you almost certainly have a lot more fouling than you think. Iosso or JB, coated on a patch, wrapped around a nylon brush. Work it down the bore in a sawing motion. Three patches total. Don't go overboard. By the third patch it should feel smooth. Clean the barrel with Butches and alcohol when you're done.
 
Not trying to take the thread in a different direction, so if the issue is bearing surface and we are assuming that a heavier bullet has a longer bearing surface, what if anything changes with some thing like the all copper bullets with multiple relief rings down the bearing surface?
 
I'm going to break from the wisdom of @Frank Green and tell you this is where an abrasive comes in. Based on my experience with 6GT, you almost certainly have a lot more fouling than you think. Iosso or JB, coated on a patch, wrapped around a nylon brush. Work it down the bore in a sawing motion. Three patches total. Don't go overboard. By the third patch it should feel smooth. Clean the barrel with Butches and alcohol when you're done.
I think you and @Frank Green nailed it.
I ran my buddies bore scope in there and sure enough the first several inches had thick carbon and copper fouling!
Definitely some scaling in the grooves, I can't see the actual first bit of lands but the rest of the barrel was sparkling clean and showed minimal wear.

I'll definitely be hitting it with more copper remover and probably bore paste.

On another note I belive I figured out what happened to the mystical flight of the disappearing Dtac...
Wifey went to turn on the sprinkler in front of my range and was piiiissed!
Gotta run my bipod higher to account for the ground swell...
20240814_202340.jpg
 
Interesting.

I wonder if this is known through empirically testing, or if its a bit of lore that has been passed down through different generations of individuals in the business.

I would be curious to find out what testing has been done.
Many bits of lore spoken of by the very experienced from times gone by end up being sound, although not necessarily following the process to effects, that the old timers thought. It comes down to how trustworthy the source is about reporting actual results, even if it’s hard to say exactly why.
 
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I should also mention I ran Butchs Bore shine through, and after analyzing 8 soaked patches there was very little to no copper staining as they dried.
I visual inspection with a light doesn't show any fowling or copper, again the borescope tonight will tell me more on that front.
And just a recap, the 112s were the initial bullets that were blowing up.
I loaded dtacs the other night and they're doing the same thing.
Hit it with Sweet's 7.62 solvent. That will tell you for sure if any copper in the barrel. If the patches are coming out blue in color.... you've got copper in it.

The Butch's especially the newer stuff doesn't seem to work as good as the older stuff based on what we see.
 
I'm going to break from the wisdom of @Frank Green and tell you this is where an abrasive comes in. Based on my experience with 6GT, you almost certainly have a lot more fouling than you think. Iosso or JB, coated on a patch, wrapped around a nylon brush. Work it down the bore in a sawing motion. Three patches total. Don't go overboard. By the third patch it should feel smooth. Clean the barrel with Butches and alcohol when you're done.
I use JB Bore Compound or 40x cleaner on a given bases. So I do use it more than you think.

No I won't use Iosso or KG2 bore paste etc...
 
Do you use brass jags with this stuff? If so, does the brass interact with Sweets?
Yes I use brass jags. Here at the shop we got some aluminum now as well but I like using the Parker Hale jags which are brass.

Yes it will react with the brass jags but I'm not letting the stuff sit with a patch on the jag in the bore. Use it and get the patch off and put a new one on and get it wet... down the bore and back and repeat.

I don't have a problem with false readings on the color of the patches because I'm using the brass jags.
 
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Hit it with Sweet's 7.62 solvent. That will tell you for sure if any copper in the barrel. If the patches are coming out blue in color.... you've got copper in it.

The Butch's especially the newer stuff doesn't seem to work as good as the older stuff based on what we see.

Have you tried Wipe-Out with accelerator? I switched to it from Sweets and find it removes carbon and copper quicker than Sweets with out the corrosion concerns.

A friend of mine talked me into the KG copper remover and I've haven't had good luck with it. I've been meaning to call them because it seems like I received bad products based on how poorly it works.
 
Have you tried Wipe-Out with accelerator? I switched to it from Sweets and find it removes carbon and copper quicker than Sweets with out the corrosion concerns.

A friend of mine talked me into the KG copper remover and I've haven't had good luck with it. I've been meaning to call them because it seems like I received bad products based on how poorly it works.
I don't use wipeout at all. Haven't found the need to.

The way I clean I have no corrosion issues with the Sweets and it cleans fast on the copper... after I dry patch the bore I follow up with the 40x cleaner most of the time or the JB. This removes or neutralizes any Sweets left over and helps better with carbon build up.
 
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Borescope is the way.

I use a borescope, a new/fresh bronze brush, penetrating oil (Liquid Wrench/Kroil/etc) and abrasives (Iosso) every time I clean my barrels now (usually every 200-300 rounds), and things have never been better on that front for me. My barrels shoot better and last way longer than they ever did when I wrongly held the opinion that the harshest thing anyone should ever use was a cotton patch and/or nylon brush along with some shit that turned patches blue.

I don't think what one uses matters as much as how one uses it, thus a borescope is an absolute necessity. I've tried nearly everything on the planet and without seeing for yourself what exactly is going on inside the barrel, you just don't know. Just because patches seemingly come out clean or patches come out blue doesn't necessarily mean dick.

That said, abrasives in the wrong hands can be a disaster waiting to happen. Don't be that guy, look at what you're actually accomplishing with your work, don't go bananas, and everything will be fine. It's like using rubbing compound to get a nasty scratch out of your car/truck, if you're careful and check your work as you go, the results can be amazing, but go too far and you'll be paying for a new paintjob.

I've got a 6CM barrel that's still shooting 3.5" groups at 750 yards with ~3000 rounds on it that would've been a tomato stake at ~1500rds if I had only been using Sweats/Wipe-Out/Eliminator/etc.

Without a doubt guys will still fuck things up by overdoing it and keep Mr. Green and places like Bugholes in business forever... but if you look at what you're doing and can resist being an idiot, if there's shit in your barrel all you have to do is scrape it out lol.
 
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