A method of making a golf ball core comprising the steps of providing a first polybutadiene pre-impregnated with at least about 50 weight percent of a first filler; providing a second polybutadiene substantially free of the first filler; providing a free radical initiator and a crosslinking agent; mixing the second polybutadiene, the free radical initiator, and the crosslinking agent with the first polybutadiene to form a polybutadiene blend; and molding the polybutadiene blend into the golf ball core.