I have been polishing a heap of brass over the past month or so, having got a good supply of crushed corncobs after somewhat of a drought and had accumulated a backlog of dirty brass.
The corn cobs have been combined with a decent glug of Nu Polish following a recommendation of a member here and the results have been excellent.
Yesterday I tumbled some 223 brass (commercial Winchester) that had been sitting for a couple of years. It wasn't particularly dirty when I threw it in(I think th eonly powder that those cases would have seen is 748). I pottered around for a few hours and went to pull it out and this was what it looked like:
I don't know what caused it, but I took it upstairs and drowned it in hot water with a decent slug of laundry detergent. I went back about an hour later and tipped it out, black flakes went everywhere. I replaced the water and there was still a good amount of soap in the brass, so I left it overnight. Here is the result:
This pic is a tad blurry, but you can see that it came good and is pretty well ready to load.
As I have around 50lb of corn cob media downstairs, I will dump the current stuff and start again.
Amazing what a wash will do.