The starting pressure of projectile, as a ballistic sensitive factor, was studied in the paper to improve the stability of the muzzle velocity. The up-to-date computer technology and high plastic finite element theory were applied in the numerical simulation of the band edging properties during the interior ballistic process. The results can explain the problem of peak interior ballistic pressure, which is a long-standing puzzle to artillery researchers. To a certain extent, this also proves the correctness of the findings. The conclusion explains the'mount value'puzzle which has been existing for a long time, this also proves the correction of the study in the paper.