Here is a fellow useing one of my ideas to make slingshot ammo you could also make sons buckshot with smaller sockets and as you can see it works great.
Cool idea. Does the irregular shape cause any drift at all ? I've been looking for a mold for making some shot.
Ya know, Lyman and several others make and sell round ball molds for front stuffers, even fishing shops sell molds for round shot, if you wanted true round shot, that's how I would do it! Still, goes to show that Lead can be molded from many different found things and it works!
I was going to suggest molds made by Do-It industries in Denver, Iowa. Yes Iowa. Man, have their prices sky-rocketed!!!. But if not abused those molds are a generational investment. Jigs, down-rigger, sinker, decoy anchor, snagging hook you name it, over 700 types.
Dad had some lead toy soldier molds I played with as a kid, I think my brother has the mold . As for making sling shot bullet molds it's easy , There are several release agents so the lead does not bond to the brass. Spent pistol rounds can serve as molds and use a kinetic bullet puller to release them or drive them out from the primer hole. One use a hard wood plug inside that may slightly burn against the molten lead and it will serve to make driving the shot out easier ,and control the bullet weight and diameter and may provide the (char) lubrication .
AS has been mentioned previously, fishing sinkers can be cast from moulds of suitable size. A bonus feature is that fishing sinkers would make a good trade item in TEOTWAWKI times. My search engine continues to weep.... discovering the joys of grapnel sinker moulding.... Grapnel Sinkers How I make them | Fishing - Fishwrecked.com - Fishing WA. Fishing Photos & Videos