It is known that the forces and shocks that occur during the firing process of a firearm induce vibrations to the barrel of the weapon and to the weapon as a whole. There are flexural, longitudinal, radial and torsional vibrations. The most important ones are considered to be the flexural or bending vibrations, especially the ones recorded in the muzzle section. This paper presents a method of recording the flexural vibrations of the barrel in the muzzle section of a 5,56mm automatic rifle and the influence of muzzle devices, using modern equipment (high speed cameras) and dedicated software.