Check Track of the Wolf. They advertise pure lead buckshot. Grafs, Midway and other advetise hardened shot. I bought mine for my 25 out of TOW for that reason. As to how they make it, the ML ball are swaged. They may "hob" buckshot to get it round, or use modern drop shot methods. Depends on your uses and needs. At squirrel ranges either would work, at a target match you may prefer the swaged. There may be no difference for all I know.
DP