Disclosed herein is a method of making a golf ball by mixing a polyisocyanate copolymer and at least one other reactant, such as a polyol, to form a reaction product and reaction injection molding the reaction product to form at least one of a core and cover component. Preferably, the polyisocyanate copolymer includes an aromatic polyisocyanate and an aliphatic polyisocyanate. Most preferably, the polyisocyanate copolymer includes a copolymer of toluene diisocyanate and hexamethylene diisocyanate.