Based on the simplifications of muzzle flow field,this paper studies the starting condition and parting movement between the sabot and the rod of a gas-propelled APDS duing the discarding process.

Based on the analysis of the incipient standard, incipient probability and exposure degree of the uniform particles lying on the surface of the river bed, the formulas to calculate the incipient condition of uniform grains on different bed slopes are put forward by using the rolling balance mode, and the calculation parameters of incipient shear stress are presented.