The engraving process of projectile had great impact on the projectile motion in the bore. By using the Abaqus/Explicit and its subroutine VUAMP, the finite element calculation of in bore motion process and the engraving process of coupled classical interior ballistic equation set of a certain fixed mounting type projectile were calculated. In addition, the finite element models of three kinds of band structure were established to be simulated. The results shows that the projectile impact engraving will lead to the sudden decrease of the acceleration of the projectile, and the overload sag of single band is more severe than that of double band with the same band width. Considering the maximum bore pressure, projectile overload change and movement resistance and other factors, a single band with 24 mm width is an ideal choice.