Been struggling with a new aluminium 4 cav 350 gr. Mold. I scrubbed out the cavities with hot, soapy water, I heat cycled it 3 times and it would just not settle and pour without those thin voids up one side or another. Good alloy that works fine in other molds. So i Lee mented it ( polished the cavities) and debured the edges with a pencil eraser. Even with all that i must really pre heat it hot and cast frosty boolits to get it to drop without voids. Maybe it will settle in over time? I'm thinking maybe the depth and spacing of the lube grooves is causing freak turbulence with the molten lead as i pour, just a geometric quirk.....