copper in bore

[Link]

What is the cause? A rough bore or soft copper jackets?
What are your thoughts?
ty Don

 

[JEFFPPC]

Normally occurring from friction and heat. It can be enhanced by what you noted.

 

[FNSafari]

Rough bore. If you have ever owned and shot a competition rifle with a finely lapped barrel from the likes of Shilen, Hart, Bartlein et. al. you will not get any copper after a proper break in. If you are using a factory rifle chances are the bore has its share of tool marks and rough spots that strip off copper or guilding metal depending on the type of bullet you are using.

 

[LHSmith]

Shooting with a dry bore.

 

[Longtrain]

+1
My competition barrels, Kreiger, Brux, Hart etc., have never shown copper after, as noted, a good break-in. However, get 2500 rounds down and the throat looks like a dry creek bed and voila…copper. For me, it’s a sign that they have entered the last stages of life, maybe usable for a while more, but you will start to see that telltale blue on your patches.

 

[Jarhead6870]

I shoot nothing but premium barrels and have no copper in the smaller calibers but when shooting the big boomers driving heavy bullets at speed, I find copper after just a few rounds. As mentioned, friction, heat and speed all contribute as well as the composition of the copper. I find Hornady’s copper more than Berger’s; no big deal, just have to clean well after a session.

 

[divingin]

A new barrel will get a lot of copper caused by the front of the chamber. The first few firings will cause the newly machined chamber to strip copper from the jacket, and the combustion gases will vaporize it. That copper gets deposited further up the barrel as the gases cool. The chamber mouth gets smoothed by the heat of firing and the copper lessens after several rounds (can be anywhere from fewer than ten to about a hundred, in my somewhat limited experience.)

 

[WVRJ]

I have a Shilen Select Match barrel in 280 Ackley Improved that I broke in carefully.This past weekend I decided to clean it because it had been close to 100 rounds since the last cleaning.The first thing I do is a shot of Outers foaming bore cleaner.If there's any copper,it usually shows up.No sign of any.Next,I use Butch's Bore Shine on a patch.No copper,and only a little bit of carbon on the patch.Next,I ran a nylon brush saturated with Butch's through a few times followed by a patch.Nothing on the patch,no copper,no carbon,nothing.Thinking there has to be something in there,I gave if a few passes with a bronze brush soaked with Butch's and ran a patch through it.The blue crap just poured out of it.Finally I got to it,I thought.I did it a few more times,and it was steady blue on the patches.It was coming from the metal on the bronze brush.There was never any copper in there.After 85 rounds,I was sure it had to have some,but there was none.I have 3 more of their barrels,and I usually clean them pretty often,usually after 40 rounds,and I don't see any copper in any of them.My 300WM elk rifle has a Remington factory barrel,and 10 rounds will leave a lot of copper in it.I have a VTR in 308 that's been lapped,but it still gets copper in it.What I don't understand is why a lot of guys say if a barrel is lapped to a smooth finish it'll copper foul.Just when you think you know a little something,you realize how much you don't know.

 

[Straightshooter1]

What is the cause? A rough bore or soft copper jackets?
What are your thoughts?
ty Don

It's more complicated than it seems, especially if one doesn't really understand the physics involved, IMHO. As I see it, with regards to gun barrels, it's the specific relationship between the barrel's metal and the projectile. There's apparently an optimum smoothness of a bore that will have the least effect on a particular copper alloy, in terms of copper fouling. On one end of the spectrum, if the bore is too smooth, then you have an issue of the copper alloy tending to fuse with the very smooth bore surface as the smooth surface actually presents more contact surface than a rougher surface. At the other end, the bore can be rough enough where it acts on the projectile like a fine file, scraping off copper material. And different copper alloy's will react differently to different smooth surfaces.

It's been a very long time since I studied physics in college, so I'm probably not explaining it quite correctly . . . particularly with regard to the fusing aspet. But if you're really interested, you can probably do a google search and find some expert explanation of this phenomenon.

 

[jelenko]

It's more complicated than it seems, especially if one doesn't really understand the physics involved, IMHO. As I see it, with regards to gun barrels, it's the specific relationship between the barrel's metal and the projectile. There's apparently an optimum smoothness of a bore that will have the least effect on a particular copper alloy, in terms of copper fouling. On one end of the spectrum, if the bore is too smooth, then you have an issue of the copper alloy tending to fuse with the very smooth bore surface as the smooth surface actually presents more contact surface than a rougher surface. At the other end, the bore can be rough enough where it acts on the projectile like a fine file, scraping off copper material. And different copper alloy's will react differently to different smooth surfaces.

It's been a very long time since I studied physics in college, so I'm probably not explaining it quite correctly . . . particularly with regard to the fusing aspet. But if you're really interested, you can probably do a google search and find some expert explanation of this phenomenon.

This is my understanding also. A key 'issue' is to recognize that 'rough' and 'smooth' are very relative when used here. The roughness and smoothness is measured at the microscopic level