The paper presents a method of applying the LS-DYNA module in Ansys software to investigate the barrel vibration when firing, corresponding to the position of the front sight near the muzzle of the barrel and at the gas block. The vertical and horizontal vibrations of the barrel at the time the bullet leaves the muzzle were investigated. The results shows that when the front sight is at the gas block, the vertical vibration at the muzzle position decreased by 23.10% and the horizontal vibration increased by 59.83% compared to the front sight near the muzzle of the barrel. The object of the research is the barrel of assault rifle with caliber 7.62 mm.