I’ve seen this before and I figured it was some excess lube (from a poor job on my part leaving lube all over the bullet nose) that was either around the neck of the case during firing or maybe blew back on the case with the very low pressure loads.
12 grains of unique in a 45/70 with various bullets.
Or maybe that the new dryer sheets that I was using was leaving some residue on some of the cases.
Either way the old dirty media and dirty brass was leaving it’s fine nasty particles all over my brass. Not every piece though. Maybe 15% of the batch. Which makes me think the lube that was on the outside of the brass during firing.
Then again It also left a coating on the inside of the Lyman tumbler bowl.
I cleaned the cases with some ballistol easy enough and the bowl was scrubbed with some alcohol and a bit of chore boy.
All clean now.
So what do you think caused this? I’m sure if anyone has seen it before it’s going to be a member of this forum.
Needless to say I’m ordering a new 50# bag of media this week. This stuff is shot.
Thanks everyone!