First of all I been casting wheel weight bullets for many years and never had this issue.Lately to streach my wheel weight supply, I tried to mix wheel weights 50/50 with range lead.My melt produced a sludge like heavy lead like substance that doesn't mix with the lead.A guess would be about 20% of the melt was this substance.Sturing didn't help,the sludge just floated back to the top of the melt.When I smelted,fluxed and poured the raw lead into the Lyman ingot mold for later use I never noticed this sludge.The mixing was in the production pot not the ingots.Any ideas? thanks hdbiker