Bore is clean.Whats the bore look like?
I think that’s what it is. I thought corrosion at first but it’s not. I didn’t get the discoloration when I ran Turkish NATO or Winchester 7.62 through it.Looks like oxidized copper? Unsure if that's possible but color looks like it.
It's common with lots of ammoWhy isn't that more common with other ammo ?
Edit: was that from tarnished or oxidized cases in the first place ?
Yeah, i have never seen it before but most of my exhaust is from bolt guns and goes out the barrel .