I doubt molds would be practical for a useful volume of shot. I recall reading years ago about a DYI drip tower. Melt the lead, it drips through holes sized to produce the desired shot size and it falls into a bucket of diesel. IIRC the height of the fall through the air and the depth of diesel the shot sunk into before hitting bottom (or the pile of previously made shot on the bottom) were the key factors is producing consitently spherical shot. Haven't the faintest clue where to start looking for such a thing though.
Dean