There are rough aluminum gang molds out there, I've got a couple. They cast two different sizes of balls, roughly .25 and .50. The results are pretty crude, rather flattened and occasionally mis-aligned. Marked on the back is: "Sling Shot Pellet Mold / C. Palmer Mfg. Inc. West Newton, PA. 15089". Mine are more than 10 years old, but I've seen them in catalogs recently, can't remember where.