A fluid jet system includes an upstream high-pressure body having a high-pressure bore axially positioned, a retaining nut configured to couple to the upstream high-pressure body, and an orifice mount assembly. The retaining nut includes a mounting chamber configured to laterally receive the orifice mount assembly without application of a torque while the retaining nut is coupled to the upstream high-pressure body and the system is at ambient pressure. A face seal may be mounted in either a downstream portion of the high-pressure bore or the orifice mount assembly to provide a high-pressure seal while the system is pressurized.