Copper fowling, reason for

[ptf18]

Fellows. Apologizes if my question is as old as... copper jacketed bullets....

I do believe that the cause for copper fouling is bore condition...mostly.

If we're talking about run of the mill barrels... not a match grade, hand lapped, etc barrel..... rather a modern made barrel that most of us have seen (borescoped).

What percent of the copper we see fowling the bore is due to "rough" leade/throat areas?

 

[LA50SHOOTER]

Fellows. Apologizes if my question is as old as... copper jacketed bullets....

I do believe that the cause for copper fouling is bore condition...mostly.

If we're talking about run of the mill barrels... not a match grade, hand lapped, etc barrel..... rather a modern made barrel that most of us have seen (borescoped).

What percent of the copper we see fowling the bore is due to "rough" leade/throat areas?

The "Leade" / Throat is where it all starts, - I've seen some barrels that "looked" kind of "rough" as far as lapped finish (or not lapped) not only shoot well but after short break-in they quit copper fouling to a greater extent. The transition at the throat is where copper fouling begins as a plasma & starts plating the bore.
This is why I use a good Smith to do my chambering work.

I've seen some Savage factory barrels that looked mighty rough when bore-scoped that not only shot decent but broke-in fine and were not copper mines.

 

[spudgun]

Humm, I get 2 areas that get copper coated. The throat and the last 2 inches of the barrel. When I know its time to de copper is when I can see it at the muzzle.

 

[msinc]

I think I understand what you are asking...if the throat is rough and you are getting copper from that, as a plasma like the way Krieger Barrels describes it then it should be heavier in the area just after the throat and evenly placed on the grooves as well as the lands. If it appears to be more smeared heavy on the lands and not so much in the grooves then I would say it is due to bore finish and/or dimensions and has nothing to do with the throat. As a plasma it can "decide" to just attack and stick to the top of the lands.
You can have both and I will say that for certain, copper fouling due to bore finish is not limited to stock or factory barrels. The last several "high end" barrels I installed all copper fouled pretty moderately and in a bore scope the bore finish looked like a million dollars.
If it is the throat I will say that I have had fantastic results with one rifle using the Tubb fire lapping kit. Otherwise, if determined to be from a rough throat then the only other fix is a re-chamber....probably with a different reamer and lube.

Edit: I don't really know why what appears to be a perfectly finished bore will copper foul, but many sure do. Maybe something going on at the molecular level, because it stops if you keep it clean and shoot it enough.
In regards to some factory barrels, you can see in a bore scope what looks like a rough file like surface that looks as if it should really peel some copper off the jacket. If this is a buttoned barrel then the reamer marks still show up, but they have been "ironed" smooth by the button as it swages in the rifling. Stock barrels are typically not lead lapped so you can always see these smoothed out marks. Aftermarket or "custom" barrels typically are lead lapped and that gets rid of these marks so they are not seen. After market barrels are NOT lead lapped just for this sole purpose

 

[Bill K]

I believe it is mostly in the make up of the metal in the barrel. I have seen some very rough bores barely show signs of copper and some very smooth one's do. I think each barrel is a different breed in it's self and you can not really gauge how it will foul or show signs of copper wash or even carbon.

 

[JMayo]

What about the bullets used. Some leave copper worse than others.
I just received a kreiger barrel that is smooth as glass. I haven't found one blemish. Gonna be a 6 ppc soon.
I hope it'll clean up like my 30 bart does.

 

[ptf18]

LA50SHOOTER and MSINC.... I think you 2 are addressing what I'm asking. Permit me to go a bit farther.

Has anyone seen a "rough" (for whatever reason its considered "rough") bore and NOT copper fowl?

2nd question. If its determined that a "rough" bore (or throat) is the cause of copper fouling how can continuing to shoot the gun (over a period of time) "fix" this issue? I ask this because I've heard that some copper fowling issues clear up after the gun is repeatedly fired.

I would think that if a clean but rough bore copper fowls, that the "roughess" is simply filling up with copper (and carbon) and maybe, at the same time causing jacket material thats been "ripped" away from the bullet to be deposited ONTO the bore...with the passage of the next bullet "pressing" SOME of this "loose" copper into the grooves and lands while at the same time pushing it (copper particles) out the bore.

If my line of thinking is correct, I would think that you would have to clean the bore after every shot otherwise your only "packing" the previous copper fowling into the bore.

Thoughts?

 

[skeeljc]

Throat roughness may be the prime factor but heat has a big influence. When I shoot in cool weather, say 50 degrees, I almost always get little to no copper fouling.

 

[6ShotsOr5?]

Humm, I get 2 areas that get copper coated. The throat and the last 2 inches of the barrel. When I know its time to de copper is when I can see it at the muzzle.

+1, I usually shoot suppressed and I see it on my mounts / muzzle brakes

 

[msinc]

LA50SHOOTER and MSINC.... I think you 2 are addressing what I'm asking. Permit me to go a bit farther.

Has anyone seen a "rough" (for whatever reason its considered "rough") bore and NOT copper fowl?

2nd question. If its determined that a "rough" bore (or throat) is the cause of copper fouling how can continuing to shoot the gun (over a period of time) "fix" this issue? I ask this because I've heard that some copper fowling issues clear up after the gun is repeatedly fired.

I would think that if a clean but rough bore copper fowls, that the "roughess" is simply filling up with copper (and carbon) and maybe, at the same time causing jacket material thats been "ripped" away from the bullet to be deposited ONTO the bore...with the passage of the next bullet "pressing" SOME of this "loose" copper into the grooves and lands while at the same time pushing it (copper particles) out the bore.

If my line of thinking is correct, I would think that you would have to clean the bore after every shot otherwise your only "packing" the previous copper fowling into the bore.

Thoughts?

Yes, I absolutely have seen rough bores that did not copper foul. I will go a step further and say that while they appeared rough and they did pick up a little copper they seemed to be easier to clean. I think it's strange too. I will also say that the two worst copper fouling barrels I have ever seen were also two of the best looking, smoothest, most flawless barrels I ever scoped. Again, yes I find this strange too, but it's true.
As to a bore that fouls badly your line of thinking is correct. First off, shooting the rifle will cause the bore to smooth out {confusing term because of what I will say later, maybe I should just say "change"} and stop fouling. In most cases it's just a matter of time {really rounds fired} before it calms down and quits fouling. That said, some never do, but thankfully they seem to be rare.
You are also correct that if a barrel is fouling badly it will just keep on smearing copper in the bore if you keep shooting and it does no good at all to keep on firing over top of existing fouling. When a bullet is fired down a whistle clean, completely copper free bore is when you are accomplishing maximum break in effort as far as the bore is concerned.
I wish I could tell you some foolproof method or way to positively and quickly stop copper fouling, but I cannot. I can for GD sure tell you how to make one do it...get some fine metal polish and slick the bore up real good and shiny...she will copper foul like you aint never seen!!!!!!!

 

[Gunnfun]

Rabbit trail warning..so in the spirit of the barrel copper fouling does it make a difference if the rifling is “cut” or hammered? Then benchmark “rests” the barrel during the rifling process.
My break in on a Nosler Trophy Grade M48 with a Pacnor barrel took 20+ rounds and several hours. It rarely picks up copper. The Howa 1500 break was 4 shots and doesn’t pick up copper.
Great topic..