Abstract: The rigid-perfectly plastic dynamic response of a slender projectile penetrating into a semi-infinte concrete target with a oblique angle was presented based on the theory of free-free beam subjected to impulsive lateral loading. The lateral and axial loading was given by dynamic cavity expansion theory. The distribution of compressive stress conducted by bending moment and axial inertial load was presented which indicated that slender EPW was sensitive to the effect of lateral impulsive loading resulted from non-ideal impact. A criterion expression, for the minimum thickness of the cartridges and the maximum oblique angle of projectile, without any bending failure and damage, were formulated in the case of hollow and slender missiles penetrating into semi-infinite concrete targets at different initial velocities and length-to-diameter ratio.