A long time ago I visited Warren Manufacturing in Arkansas. One of their products was cast round ball. I guess they used a casting machine and then they tumbled the ball. I think graphite was added to the mix at some point as well. The last man to leave the plant put the ball in a series of tumblers and it was tumbled overnight. Then they would package them the next morning. IIRC, it made for a good looking ball. Problem was with consistency. In a box of 20 large diameter (.678 to .715") there were probably 4 or 5 different diameters. In my sporting rifles they shot OK, but I finally decided to cast my own for a tighter control of the output. I used the brass moulds from England. Those were great.