Depick
.308 Win
I will give that a try.Mystery solved.
ETA. Will you be using a vibratory tumbler or wet tumbling? If you're going to use a vibratory tumbler this may not even be an issue after your first firing. Reason being, a vibratory never gets the casings 100% clean. The carbon will act as a lubricant. The brass will also be a bit more worked and elastic. As an experiment, if you still have some casings you didn't load up yet, try sizing one and then lubing it. Make sure to get the inside. Clean the expander bell off thoroughly. Then bell the casing. If you still get some shavings/brass dust the bell is definitely slightly out of spec/rough. Polishing it would still be the solution to the problem.