Copper discusion

[chet]

So, we all know that copper fouling is caused by rough tooling marks in the throat. These tooling marks are un-avoidable as they come from the chamber reamer, long after the barrel is rifled.
Those rough spots take copper from the bullet, the copper is then vaporized by the burning gasses and it is deposited all along the bore.
HOWEVER, I believe that at least some of the copper fouling that exists near the muzzle is caused by friction. Keep in mind that this is where the bullet is traveling at it's highest velocity.
I also believe that this is why copper at or near the muzzle can be a bear to remove. If it was merely deposited there, it should wipe away with ease, right?
Yes, I'm having one of those moments when all I have to do in life is think about stuff like this 8)

Any thoughts on how I can test this theory?

 

[Ridge_Runner]

my take on it is in a typical barrel there would be more machine marks in the rifleing because the chamber is cut, button rifled barrels are just ironed in basicly. Think about it, pulling a hardened steel oversized spud through a steel tube to iron in the grooves would do some to alot of micrscopic tearing as the spud hit slight variences in bore diameter. if you lap a barrel copper fouling is greatly reduced.
all my long range customs get cleaned around every 20 shots, they are 2 lilja barrels and 1 kreiger, all were lapped by the makers. If I use a nylon brush when scrubbing I very seldom get even a hint of blue on the patches. I do however get alot of blue from my production barrels.
RR

 

[Antelope_Sniper]

Chet,
I'm inclined to agree with you. It's very common to get a large copper deposit 6-8 inches from the chamber. This is caused by the vaporized copper you mentioned. In some rifles you will also get a significant deposit at, or 4-6 inches back from the muzzle. Is this due to the rapid cooling of any remaining vapor as the air hits it, imperfections in the barrel, or something else? It's also reasonable to think friction is a contributing factor to copper build up. A pill moving 3K+ down a barrel, fitted so tightly that the rifling is ingraved into it, creating enough heat to warm the barrel steel in 3-4 shots. Not all of that heat is from the gunpowder.

In general, with Nosler bullets, I notice a significant jump in copper deposits at velocities above 3k FPS. I've shot the heck out of rifles with loads in the 2750 range, and had very little copper deposit. Jump them up to 3100, and they need a copper solvent after 20 rounds in a production barrel.