In order to compare and analyze the engraving process of projectile in a big bore gun with different bore cone angles, smoothed particle hydrodynamics (SPH) method was used to simulate the engraving process of projectile band under a certain charge condition. The engraving resistance and driving torque are obtained by simulation, and the causes of torque fluctuation are analyzed, and the improvement measures to reduce the torque fluctuation and relieve the rifling force are put forward. The results show that the study can provide a reference for the study of the influence of the cone angle of the slope bore on the groove of the ammunition belt.