have you ever seen a mold at will only cast properly when completely cold ?

[Smoke4320]

have you ever seen a mold at will only cast properly when completely cold ?
I have a RCBS Mold that will only throw good bullets if the mold is cold.. after about 5 to 7 casts it will have a heat induced shrunken and frosted area ..
same area every time and on both cavities..
I have tried lead temps from 650 to 725 degrees and the hotter the lead the faster the shrunken area shows up ..
tried preheating the mold and got them within 2 casts ..
lead is 98% coww and 2 % Hi speed billet (for the tin and little copper)
ideas?

[JonB_in_Glencoe]

I see that especially in longer boolits.

The problem is that your mold is not uniformly up to temp. Or more simply, you have a hot spot in the mold. you need to preheat the mold up to temp so it has NO hot spots or cold spots. I like my boolits to have a light but uniform frosting. Boolits with frosting in the middle or in the middle on one side and shiney on either end or both ends will NOT be symmetrical.
Good Luck,
Jon