Copper Fouling

[tkcomer]

What exactly is the effect that copper fouling does to lead bullets? I see a lot of posts on getting all the copper out of a rifle barrel before shooting lead, but I never did know how the copper affected the lead bullets.

[felix]

Any kind of fouling hurts cast more because cast cannot generally push junk away. Softer the boolit/bullet, the more the barrel scraping is required for the cleanest next shot. Also, for higher lands, the scraping required is minimized. ... felix

[tkcomer]

So the copper damages the cast bullet?

[felix]

Likely, but sometimes not, all depending on the barrel and projectile factors spread about the board's threads. The only way for sure is to shoot the gun and see if the accuracy is OK for the gun's application. ... felix

[docone31]

Fire a few and see.
It is fouls, then Hoppes #9 and lots of elbow grease. Actually it is not that hard.
I have loaded got miserable accuracy, went home, did the elbow grease thing, fired some more, went home did more. Eventually I got the lead out so to speak.
I then used lapping compound on the castings. After sizeing them, I rolled them in valve lapping compound. fired about 20, lightly smeared. Not only no copper, but no hammer marks in the bore either where there had been some previously.
That is my way. Works for me.
Fire it first though. Sometimes that copper comes out real fast.

[tkcomer]

I'm just trying to figure out exactly how copper throws cast bullets off. “Everyone” says copper fouling affects cast bullets in the accuracy department, I'm just trying to understand why.

[docone31]

It interferes with the path of the casting. Rather than going down a slick tube, it is rough. This modifies the shape of the casting, and introduces defects in the casting.
So many reasons, the main thing is as the lead builds up on the copper, your accuracy will go out the window.
Fire it. It might not be an issue.