The concept of a gun launched micro air vehicle (GLMAV) is currently studied at ISL. A micro air vehicle (MAV) packaged in a projectile is launched using the energy delivered by a portable weapon. When it reaches the apogee the projectile is transformed in such a way that the MAV becomes operational over the zone to be observed. A light projectile of 80 mm caliber has to be launched with low velocity: 57 or 100 m s−1. To achieve these velocities a very low pressure in the tube is needed. Hence the GLMAV launcher is designed as a two chambers system. Propellants and igniters are enclosed in a small high-pressure canister, which is connected to the tube with the projectile (low pressure chamber) by vent holes. The charge consists of two propellants in partially separated volumes; the fast burning GB propellant ignites the slow burning L1 propellant. The interior ballistics of the GLMAV launcher is solved by the zero dimensional model STANAG 4367 with an extension for the two chambers system. Calculated pressures in the high and low pressure chamber and the muzzle velocities are compared with ISL measurements. Although the used theoretical model cannot describe correctly all specific features of the GLMAV launcher, the differences between the calculated and measured maximum values are up to 10 %.