A metal alloy is heated to a molten state, and a grain refiner may be added. The molten alloy is poured into a shallow chamber of a shot sleeve of a vertical die cast press and on top of a shot piston. The shot sleeve is transferred to an injection station while the molten alloy cools to a semi-solid slurry with a globular, generally non-dendritic micro structure. An inner portion of the shallow slurry is injected upwardly by the piston through a gate opening into a die cavity while an outer more solid portion of the slurry is entrapped in an annular recess. After the slurry solidifies, the shot piston retracts, and the shot sleeve is transferred to a position where the residual biscuit is removed. The shot piston may have internal grooves to provide a large heat transfer area for cooling water to absorb heat from the molten alloy.