With a bunch of reloading stuff I picked up came a small box with RCBS priming scribbled on it and this stuff inside:
What's it go to?
Doesn't fit my Rockchucker, Lyman T-Mag or my RCBS A3.
Way to thick and shaped differently.
It's .365 thick.
Too good to throw out, but have no idea what I'll ever use it for when I don't have a clue what it goes to.