Just about every barrel I have had that was nitride coated has had a orangish brown fouling when wiping out a brand new barrel. This one is no different.

Here is the thing. I have done 5 soakings with the older cans of gunslick foam cleaner. I still had what looks like copper fouling. Sort of. The color is off for what I normally see with copper.

So, I broke out the Sweets 7.62 cleaner. I soaked the bore for 15 minutes and cleaned it out. I did this twice. And whatever the fouling is, it is not coming out. I then got out a brand new brush and some Amsoil bore cleaner. I scrubbed the barrel for about 25 strokes and then ran patches till it was almost spotless on the patches.

The fouling is still there and has not changed at all. The foam always leaves a blue slime on the rag I set the barrels muzzle down onto. I use that as a indicator of how much copper is in the barrel. And nothing showed on the patches with Sweets either.

Would this be some kind of hard oxide that formed during the nitride treatment?