Carlucci et al. (2013) proposed a theoretical model describing exit vibrations of a shell launched by a gun. The model treats the shell as a system of a spring, damper and a rigid mass. In this paper, similar models describing vibrations of shells and monolithic projectiles are compared with some 1D models taking into account wave reverberations. The comparison proves that the models taking into account the wave motion, forecast similar amplitudes and frequencies of vibrations as discrete models. However, details of acceleration time courses differ considerably. The problem of the influence of the friction force between the shell wall and the filling is also discussed. The results of modelling serve as well for assessing if some projectile velocity oscillations detected by making use of the Doppler radar can be solely attributed to the exit vibrations.