wall 14 the pressure exerted in this way on the liquid medication causes a collapsing of flexible container wall 14 and this drives the liquid medication through jet orifice 18 at high velocity peak pressure up to 300 bar occurs at the beginning of the injection and forces a jet of liquid medication to penetrate through a skin layer and thereby form a fluid delivery channel into the subcutaneous tissue the pressure then drops to about 100 bar to complete the medication injection through the so formed fluid delivery channel ease of jet penetration varies between patients or between injection sites on the same patient the initial peak injection pressure is therefore adjusted to control the jet penetration force to an appropriate value this adjustment is effected by positioning co volume seal ring 34 at a suitable axial position with respect to cartridge shell 12 in order to set the value of the annular co volume 28 increasing co volume 28 increases the expansion volume of the gas generated and delivered by the gas generator and reduces the initial peak pressure to a lower value a co volume setting ring 48 that is part of the application device described hereinafter slides into the rear of cartridge 11 during loading of cartridge 11.