Quote Originally Posted by bigbore
Can you explain copper fouling to me like I'm 4 years old?
I don't know if I can explain anything to anyone in those terms

Nor do I think that I can share anything about barrel fouling that you do not already know, but here is what I do know. Jacket fouling is a result of two things, the first being the jacket material that is released from the bullet in the initial stage of the shot, this occurs as the "gases" are actually in a plasma state and heat the jacket to the point that copper is released into the plama state.

This is a more like a plating really, it occurs in the very first part of the barrel throat and bore and is generally very uniform in deposition.

After this, the more traditional form of fouling occurs as the gilding metal galls in the bore; these patches of built up copper cause differences in the friction that is applied to the bullet as it travels down the bore. This friction can "tear" at the bullet's jacket and deform the base of the bullet, causing it to be unstable in flight.

Now, how often does it occur and at what point is it an issue? I have found that barrels are a lot like people in this matter; just like some people have a natural propensity to be artistic, athletic, or whatever... some barrels will foul more than others -- there is no hard and fast rule as to what make a barrel more or less likely to be a "fouler", but bore surface and consistant/correct bore diameter certainly play a big part in it.

As you know, there are the odd occasions where a barrel can not go a half dozen shots without throwing rounds all over the place... a good cleaning and it is back for a few more rounds, but fouls out just as quickly -- I think the name for these is "lemon" or "junk"?

And as you know, some rifles can go hundreds or thousands of rounds with little effect on accuracy from fouling -- when a shooter makes his first shot, it is called a Clean Cold Bore (CCB) shot, professional shooters even have seperate dope for this... oddly enough, the CCB shot is generally not the most "efficient" shot, as thin films of lubricants can increase the force needed to push that first shot and the cold bore is "tight" -- this CCB shot generally will have a higher recorded peak chamber pressure than the follow-up shot, I have known guys that even put a round in the ground before a patrol for a "fouling shot" (and other reasons).

As stated, bore surface is a primary suspect in a fouler... lapping and plating are thought to be preventive measures and record books support this.

To answer your question though, fouling is a concern if it is a problem (how is that for a cop out!) -- with most "practical" guns, fouling will reduce accuracy so little that it is not noticed... we can always blaim that one "flyer" on fouling though -- benchrest shooters can give themself ulcers worrying about it, but most of us don't have to worry that much, the potential for the group opening can still be covered by the illuminated dot in the optic sight...

As for the "blue patches" as a litmus test for copper... that can be very deceiving, it takes very little copper to make those patches blue and a lot of that fouling resides in the corners of the rifling, where is is doing little harm.