Abstract: This study investigates the effect of the aerodynamic jump phenomenon on the flat-fire free flight trajectory motion of projectiles launched horizontally at various angles from low-speed helicopters. The ammunition used was the 30-mm-diameter XM788 projectile type fired from M230 machine automatic cannon. Modified linear 6-DOF flight simulation modelling was applied to the free-trajectory prediction of spin-stabilized projectiles. This analysis includes variable coefficients of the most significant aerodynamic forces, moments, and Magnus effects, which have been taken from official tabulated database, in addition to gravity acceleration. During the entire atmospheric flight the coupled epicyclic pitching and yawing motion analysis is taken into account.