As mentioned in another thread, I did some lapping of a mold that was dropping undersize bullets, which worked reasonably well. I left my lapping tool in a bucket of water I was water dropping bullets into. When I came back to these bullets a day later, having let them dry, there was a good bit of powdery looking stuff on them, the grinding compound I assume.
Didn't think much of it beyond that the bullets were scrapped, so I threw them all back into the pot along with my used lapping tool and remelted them. Then it occurred to me that this might not be a good thing. I don't really want grinding compound in my bullets scouring the rifling out of my barrel. With that in mind, I fluxed my melt, a lot, and skimmed it. A lot. FWIW and in case it matters, I'm fluxing with wooden paint stirring sticks.
I poured bullets with this melt into my recently lapped mold. I guess they are ok, but it's kind of hard to tell. The bullets are somewhat textured because my Leementing is not complete, the cavities still don't have a super smooth finish. I'll do some casting with this batch of melt into one of my very smooth 357 molds to see if it still comes out looking textured, but I guess my question is, how big of a concern is this really? Will skimming and fluxing take care of the lapping compound like it would any other impurity?