From time to time I have struggled to get the bases of my cast bullets to fill out completely. The defects can vary from slight but uniform rounding of the base to irregular voids at random locations around the base of the bullets. Sometimes this affects only some of the cavities in a multi cavity mold. I have generally been able to overcome these challenges by increasing the temperature of the mold or alloy, adjusting the sprue plate, or by varying the method of delivering the alloy to the mold.
This week I was having particular difficulty filled out bases on my bullets with a two cavity RCBS 30-165-Sil mold. I was using linotype alloy. Nothing was working when I stumbled on to a new technique I will call "topping off the mold". This consists of filling the first cavity, filling the second cavity, and then in succession going back to the still molten puddles and adding a little more alloy. This method resulted in consistent perfect bases. The only downside was a slight increase in lead spilled off the sides of the mold that was then collected and put back into the pot.
Hopefully others will give this a try if they are having problems with bullet bases. I would be interested in any comments on this technique
