I just bought 1000 new, Nickel Federal .45 ACP brass, primed. Inside the case mouth on every one of them, there is a 1/8" wide black band( looks like paint) that circles the entire case mouth. On my Dillon 550B loader, when the powder funnel drops into the case mouth, it also bells the case mouth out to accept the bullet. On the down stroke everything is fine, on the up stroke this black crap sticks to the powder funnel, and I mean it holds it tight. Enough up pressure and it will snap free, which causes the powder to jump out of the case. Lubing the case mouth does nothing but make a big mess causing powder to stick to the funnel. I have never seen this on any case before. Any idea of what it is and what it's for?