I have had this same problem on and off for a long time. I just cant get the trash out of the lead. I have used Missouri bullet alloy, Rotometals 92/6/2 and 20 to 1. Beeswax, Marvelux, letting it sit, fluxing over and over even tried not fluxing. After all this there is still trash in my bullets. Occasionally the bullets come clean but not often. I have posted of this problem before and have never found a solution. Also cleaned and replaced pots. Nothing works. There surely must be a reason . Any suggestions from any of you?