That's something new to me but I don't shoot or load for slip-a-matic pistols. I can see where it could be a handy tool to use though. Is the ring right above the extractor groove in the picture similar to the problem that you are having? Is this works I would like to know, might be able to help somebody else out down the road.

I'm wondering too that if you are getting a ring like that on your brass if you might be resizing your cases too much? When I resize for a bolt action rifle I back the resize die off and then just size the brass just enough for a snug fit. Then turn the die down another 1/8 turn for just a clearance fit when the bolt is closed on a loaded round. This keeps you from over working the brass and it will last much longer.

RHB