a method of producing a perforation pattern in a slab of thermoplastic propellant material and the material produced includes subjecting the slab to a perforating press operation in which the press has a patterned array of fixed perforating members arranged according to a first pattern coordinated with a system for advancing and incrementally indexing the slab through the press is used to perforate the slab to create a desired second , denser perforation pattern by subjecting the slab to a series of perforation actions by the patterned array of perforating means coordinated with the indexing of the slab through the press .