The effect of the particle size of zirconium on the thermal behaviour and firing characteristics of Zr/KClO4 primer mixtures was studied by thermoanalytical techniques. A pilot-scale process was developed for preparing pressure cartridges whose primer mixtures had different particle sizes of zirconium. The firing characteristics were evaluated by Bruceton's method and its related calculation. It was found that the Zr/KClO4 primer mixture with average particle size of 3 or 5-mu-m is a suitable primer mixture for 1 A 1 W-1, 5 min, No-Fire pressure cartridges.