I did these too... as my dad had an auto repair shop at the time I used the expensive Prince August bars mixed up with tire weights. Yay, health hazard!

Even if you used only the fine metal purchased in the hobby shop, the models would come out a little soft in the detail. I was about 10 years at the time though, I'm sure an adult would get better results by controlling the heat of the molten lead. Also, the models are a tad small. 25mm, not heroic at all.
Scurv: The process is simple. Powder the split mold with talcum powder, clamp it together and pour in the molten metal. Move the mold about a bit and then wait for the metal to cool.