Just wanted to add one more option, for those looking at casting buckshot: I use a Lee .30 cal two cavity roundball mold. It throws a .310 pellet, which falls right between #0 and #1 buck. I get about 98% good casts, and the mold is able to cast quickly, dropping the shot out fast. I load 9 of these over various wad and powder combos as a 1 1/8 ounce 1100fps, low recoil defensive round.
As an added bonus, shooting .310 cal roundballs out of .30 cal rifles is fun. 5 grains of Red Dot or another fast pistol or shotgun powder gives 22LR velocities. I do this with 30-30, 308 Win, and 7.5x55. Lets a centerfire rifle function as a 25 yards tin can plinker or pest eliminator.