Conventional vacuum casting technique is suitable only to propellant slurry with low viscosity (< 16 KP), grains with simple geometry and sufficiently large annular space between mandrel and motor case (web thickness). To overcome these limitations, pressure casting technique is adopted. The present paper gives details of pressure casting technique and its advantages over the other casting techniques. The rheological behaviour of propellant slurry and the methodology for calculation of pressure deop during pressure casting is described. This procedure is illustrated for pressure drop calculation during pressure casting for a typical rocket motor. The pressure drop in the rocket motor is also calculated using CFD software Fluent.