The phenomena or mechanisms responsible for the ignition pressure spike, pressure rise rate, instabilities, and pressure oscillations often observed during the static tests and the actual flights of a certain class of dual-thrust motors (DTM) was studied. Inert simulators of solid rockets were selected to examine the occurrence of the internal flow choking at the subsonic inflow conditions without complications arising from the propellant combustion, using computational fluid dynamics. It was observed that, there was a possibility of the formation of shock waves in HVT motors with divergent port due to the formation of a fluid throat at the beginning of the turbulent transition region induced by area blockage.