Abstract: A method for molding composite structural plastic components is disclosed wherein such components are cast from a polymerizable thermoset or thermoplastic composition in a conventional metalcasting mold. In the instant invention, a low viscosity thermoset or thermoplastic composition having reinforcing fibers distributed therein is poured into conventional metalcasting molds, obviating the need for high heats and pressures associated with injection or compression molding of composite materials as taught in the prior art. In the case of a thermoset resin, the object to be fabricated is fully cured by the action of a catalyst at relatively low exothermic resin temperatures. In the case of a thermoplastic resin, curing is generally achieved independently of high added heat and pressure. If using a thermoplastic such as nylon 6 in the present invention, a preferred method of use involves the addition and combination of fiber reinforcements while the nylon 6 resin is being manufactured.