I recently bought the Lyman .58 caliber minie ball mould for my original 1861 rifled musket. Last night I finally got the pot out and cast a pile of boolits using lead smelted from stick-on wheel weights (the softest lead I have). As normally happens when I cast, the first few went right back into the pot because the mould wasn't heated up enough just yet, but after a while they started dropping out nicely.
They were bright, shiny, fully filled out, and no frosting. In fact, this was the best batch of boolits I've cast in a while!
After they cooled and I was able to handled them, I discovered that more than half had air pockets right inside the skirt at the top, right where the pointy thing goes to make the hollow base shape. More than half!!! They all got culled to be remelted and cast again later.
I assume this is either a temperature problem, or a technique problem. How do you all prevent this?