(57) A slurry casting process is described capable of producing crosslinked double base propellant having improved burning rates and high specific impulse. Such propellants can be formulated to be smokeless, Improved burning rates are achieved by incorporating into a slurry of double base composition, casting powder granules containing 20% to 75% by weight of small particle ammonium perchlorate. The casting powder granules substantially retain their identity in the cured propellant matrix. The casting powder granules have a high burning rate and are uniformly distributed throughout the propellant. The granules are responsible for increasing the burning rate of the entire crosslinked double base propellant composition of the invention.