Here's a trick to improving the weight consistancy of your cast bullets - overpouring.
I honestly don't have an explanation for it, but it works.
With a Lee mold, I pour an entire ladle of lead into/over each mold cavity. The cavities inevitably overflow, but I keep pouring until the ladle is empty. Re-dip the ladle and fill the next cavity.
I used to pour enough lead until a nice puddle formed on top of the sprueplate, then move on to the next cavity and do the same. Then I would wait until I could see the lead "freeze", cut the sprue and drop the bullets/balls. I thought by maintaining a puddle of molten lead on the sprue plate this would give sufficient reservoir to prevent the cavities. BUT IT DOESN'T?!?!
I'm truly confounded why my old method doesn't work as well at the overpouring. But if I weight the balls out, the old method produces a much wider standard variation than overpouring. For a 0.530" ball the overpouring method will produce better than 95% within + or - 0.3 grains. The "puddle" method produces 25% more than a full grain lighter than the rest.
The theory goes that as the lead in the cavity cools it shrinks, drawing in molten lead from above. If this molten lead is not present, it will form a cavity. But in both the overpour method and the "puddle" method, the molten lead IS present. So why such a difference?
I truly recommend a balistic balance or scale. Don't be afraid of the cheapy little $20 balances, they work great and they aren't that slow. They are only slow if you are trying to get the exact weight of each ball. But in reality your are just looking for "odd-balls" so-to-speak. So you just set the balance to your minimum acceptable weight, then run the balls through one at a time. If the balance shows less than the minimum weight - back in the melting pot it goes. Everything that "makes weight" is good for competition.