The determination of pressure profiles behind a projectile has been a subject of investigations for more than 70 years. For lumped parameter models it was especially important to determine the pressure on the projectile base, pressure on the chamber base, and pressure for the propellant burning law. In the paper two analytical methods and one numerical method are considered. The analytical methods of proportionate expansion and two-phase mixture are studied. Pressure profiles are also computed numerically by TWO Phase Interior Ballistics (TWOPIB) code, which is based on the model of two-phase flow of solid propellant and its products of combustion, treated as separate phases with appropriate conservation laws and interactions between phases. Through comparison with experimental results on the real weapon system TWOPIB code showed great advantages over analytical methods.