At the daily bulletin there is an article about barrels increasing in velocity at 100-150 round count.
http://bulletin.accurateshooter.com/2018/06/tech-tip-velocity-increase-in-new-gun-barrels/ It was also suggested that a barrel later step changes to slower again (near it's end).
Theories were brought in about why, without actual conclusions. A comment suggested managing of copper fouling.
I'll toss in my notions about it here, and hopefully we could solve this with discussion.
To begin, I dismiss copper fouling from cause, and in any way benefiting to shooting results.
Best barrels copper foul least, it's very easy to remove and maintain at low traces throughout such a barrel's life. Barrels shoot very well with no copper fouling at all.
There is no permanent copper layer at ~100-150 rounds, that would stay in a bore for it's accurate life beyond. And there is no reason to attempt creating and managing something like that.
As far as bullet jacket damage going on until ~150rnds? What is that: bad bores, bad machining, no lapping or barrel break-in? Would Speedy engage in that kind of mess? I wouldn't understand that.
I use Speedy's own declared cleaning method & see that it works with a Hawkeye, just like he does.
He would see and know a specific cause for jacket damage, and I'm confident he would do something about that immediately. I would, and I'm not even a competitor.
Speedy so consistently sees MV changes ~100 shots, that he goes ahead and does a 100sht break-in right off the bat. Apparently he believes it's break-in.
I don't know how old the article is, or if he knows today that he can break-in a bore with 10shts of Tubb's TMS. But I'm sure his observed velocity increase would still happen just the same. Same round counts. Because I don't think the velocity increase is due to 'rounding of lands' or decreasing bullet jacket damage.
I also do not assign so much causal credit to bullet friction. After all, the step change mentioned was ~80fps, and you can't cause this with a simple frictional change. Try it, you'll see, and likely see that you can't cause ANY change to MV -with friction adjustments. Don't use moly for such a test, because moly does not lower velocity due to friction. Use another friction coating/adjustment.
I use Tungsten Disulfide (WS2), which has a way lower friction coefficient than moly. I dry film lubricate both bore & bullets. This serves to provide stable fouling, pretty much eliminates copper fouling, and yet it causes zero change to muzzle velocities over uncoated bullet/bore. It also cleans right out, like carbon, but way easier than carbon.
This leads to my belief about barrel life cycles.
I think it's all about carbon.
We have a lapped surface profile in our bores, with pores that open and are eventually packed full with carbon. It's polished at the surface, mirror like, and very hard to distinguish with a borescope. It doesn't dissolve, and that packed in these pores/crevices can't be washed away with surfactants. It would have to be dug out to be removed. Steam cleaned, or something on that order. We don't dig that much as doing so would ruin the bore, or take you back to where you were before ~100-150 shots (unstable).
I think the carbon filling would show as a pressure increase -to stable (what we want).
With this, you enjoy your accurate barrel life, and then accuracy later step changes away. I'm sure this change would show with a strain gage as well.
The ultimate killer of a bore is constriction. That carbon keeps packing into all surface openings throughout a barrel's life until an early constriction swages bullets, leaving them undersize beyond as they continue down the bore. It's early in bullet travel because the first few inches take the most heat, open the surface most, and get carbon packed the most.
The common lake bed surface is thought of as jacket damaging, but I doubt that's THIS PROBLEM as our guns shoot through it just fine. And even if you J-B this to smoother, it WILL eventually turn into a constriction and kill your accuracy. Time to set back your barrel -for a couple hundred more accurate rounds, then you'll be right back to constriction. This is the end of accurate barrel life.
It's like a switch flipped, and those at a cutting edge performance can see it within 20rounds of it's happening. Well, they might deny it, and tail chase for another 50, for the first 5 or so barrels.
Anyway, interested in ideas/observations here. Any tests about my notions that fail.
Thanx for your time.
http://bulletin.accurateshooter.com/2018/06/tech-tip-velocity-increase-in-new-gun-barrels/ It was also suggested that a barrel later step changes to slower again (near it's end).
Theories were brought in about why, without actual conclusions. A comment suggested managing of copper fouling.
I'll toss in my notions about it here, and hopefully we could solve this with discussion.
To begin, I dismiss copper fouling from cause, and in any way benefiting to shooting results.
Best barrels copper foul least, it's very easy to remove and maintain at low traces throughout such a barrel's life. Barrels shoot very well with no copper fouling at all.
There is no permanent copper layer at ~100-150 rounds, that would stay in a bore for it's accurate life beyond. And there is no reason to attempt creating and managing something like that.
As far as bullet jacket damage going on until ~150rnds? What is that: bad bores, bad machining, no lapping or barrel break-in? Would Speedy engage in that kind of mess? I wouldn't understand that.
I use Speedy's own declared cleaning method & see that it works with a Hawkeye, just like he does.
He would see and know a specific cause for jacket damage, and I'm confident he would do something about that immediately. I would, and I'm not even a competitor.
Speedy so consistently sees MV changes ~100 shots, that he goes ahead and does a 100sht break-in right off the bat. Apparently he believes it's break-in.
I don't know how old the article is, or if he knows today that he can break-in a bore with 10shts of Tubb's TMS. But I'm sure his observed velocity increase would still happen just the same. Same round counts. Because I don't think the velocity increase is due to 'rounding of lands' or decreasing bullet jacket damage.
I also do not assign so much causal credit to bullet friction. After all, the step change mentioned was ~80fps, and you can't cause this with a simple frictional change. Try it, you'll see, and likely see that you can't cause ANY change to MV -with friction adjustments. Don't use moly for such a test, because moly does not lower velocity due to friction. Use another friction coating/adjustment.
I use Tungsten Disulfide (WS2), which has a way lower friction coefficient than moly. I dry film lubricate both bore & bullets. This serves to provide stable fouling, pretty much eliminates copper fouling, and yet it causes zero change to muzzle velocities over uncoated bullet/bore. It also cleans right out, like carbon, but way easier than carbon.
This leads to my belief about barrel life cycles.
I think it's all about carbon.
We have a lapped surface profile in our bores, with pores that open and are eventually packed full with carbon. It's polished at the surface, mirror like, and very hard to distinguish with a borescope. It doesn't dissolve, and that packed in these pores/crevices can't be washed away with surfactants. It would have to be dug out to be removed. Steam cleaned, or something on that order. We don't dig that much as doing so would ruin the bore, or take you back to where you were before ~100-150 shots (unstable).
I think the carbon filling would show as a pressure increase -to stable (what we want).
With this, you enjoy your accurate barrel life, and then accuracy later step changes away. I'm sure this change would show with a strain gage as well.
The ultimate killer of a bore is constriction. That carbon keeps packing into all surface openings throughout a barrel's life until an early constriction swages bullets, leaving them undersize beyond as they continue down the bore. It's early in bullet travel because the first few inches take the most heat, open the surface most, and get carbon packed the most.
The common lake bed surface is thought of as jacket damaging, but I doubt that's THIS PROBLEM as our guns shoot through it just fine. And even if you J-B this to smoother, it WILL eventually turn into a constriction and kill your accuracy. Time to set back your barrel -for a couple hundred more accurate rounds, then you'll be right back to constriction. This is the end of accurate barrel life.
It's like a switch flipped, and those at a cutting edge performance can see it within 20rounds of it's happening. Well, they might deny it, and tail chase for another 50, for the first 5 or so barrels.
Anyway, interested in ideas/observations here. Any tests about my notions that fail.
Thanx for your time.
