An irregular burning phenomenon arises in some solid propellant motors(SRM), where the time-averaged pressure differs largely from that dedicated by instantaneous area burning. This phenomenon is generally considered the result of the interaction of pressure disturbances within the motor cavity with solid propellant deflagration. Hence, it is a combustion-dependent acoustic phenomenon. Historically, different suppression devices included the classical resonance rods and paddles, and arrays of acoustic resonators and various baffle arrangements were applied. In this paper, irregular burning which arises in a modification of a shoulder-launched rocket is investigated. Several techniques dealing with the irregular burning problem were attempted. In each case, the signal of pressure was analysed in the time domain through time average and AC pressure signal, and in the frequency domain through Fourier transform and power spectral density. The most successful technique was the drilling of holes through the grain, connecting the perforation to the external burning region of the cylinder. Next was the increasing of blocking factor, both methods lead to stabilizing the modified motor.