A modified gas delivery cartridge. A conventional straight-sided brass cartridge case is primed and then filled with solid propellant. A burst cup is then inserted in the case mouth. The burst cup is embossed with a cross or other shape to promote predictable rupture. Once the burst cup is in place, the upper edges of the cartridge case are rolled over the burst cup. In operation, the propellant is ignited to produce pressure within the sealed case. This pressure builds steadily until the embossed cross in the burst cup ruptures. The propellant gases are then vented in a metered fashion through the ruptured burst cup. However, the burst cup is retained by the case so that no solid object escapes the high pressure cartridge. In addition, by carefully designing the shape of the burst cup and the components surrounding it, it is possible to create an efficient expansion nozzle to better meter the propellant gases.