This paper describes the problem of the behavior of the truck 6x6 during the firing process from an antiaircraft gun 40 mm, which is integrated on this vehicle. The calculation of the center of gravity coordinates and the reactions of the supports of the vehicle with an integrated gun is shown. Internal ballistic calculation determines the maximum recoil force. The behavior of the mobile platform is presented using a mathematical-mechanical model of platform oscillation, which was formed on the basis of the classical principles of the theory of vehicle dynamics. With the adopted simplifications, the system with a large number of degrees of freedom is reduced to a system with three degrees of freedom, whose generalized coordinates are: vertical position of the system T, rotation around the transverse axis (galloping) and rotation around the longitudinal axis (rolling). MATLAB software package was used for calculation. Generalized coordinates changes over time, as well as the velocity of these coordinates, were determined. The analysis determined that the position of the anti-aircraft gun on the vehicle is favorable, because the system easily supports all the loads caused by the firing and the weight of the weapons, and it also allows obtaining small oscillation values, which are easily dampened by the elastic suspension system.