why does lead boolits turn black when cleaned in corn cob media?

[chaplaincolby]

I have about a dozen reloaded rounds of 9mm Mak with commercial cast boolits that accidentally got run through a vibrator cleaner with dirty brass. I don't want to get a long discussion started about vibrating loaded rounds being safe or unsafe, I just want to know why the cast boolits turned black?

[Bohica793]

I won't comment on the safety of vibrating loaded rounds, but the blackening is caused by the fact that your rounds are getting powder coated. I did this with some 147gr 9mm loads and the rounds would not chamber consistently afterwards as the nose profile was now off. Don't be surprised if you start having failure to feed.

[chaplaincolby]

What kind of powder has coated the boolits, is it the dirt in the media?

[Bohica793]

My guess is dust off the media itself. I didn't spend time figuring it out, only enough to make sure I never made that mistake again.

[CHeatermk3]

If it's black it's prolly the fouling the media removed from the cases which then stuck to the bullets due to whatever lube is on them.

If you put some dryer sheet in with the media it should attract and hold most of the black stuff--don't know if it'll help with whatever's already on the bullets but it may be worth a try.

[1911cherry]

I had some that got damp , dew fell on em, and turned black. I really don't know what in a tumbler would do it though, lead will go straight to the bottom, dirt maybe?

[RED333]

I tried a few cast boolits in egg shell, it is what I use, I do have 33 chickens.
I will not do it again, egg shell became impregnated in the lead, I just remelted and recast.
Egg shell does do a good job on brass.