Abstract: The invention concerns a guided munition, fired from a launching system with a cannon effect. This munition comprising sub-assemblies is supported, during acceleration in the cannon, by a peripheral casing which rests on the first sub-assembly of the munition placed at the front of the munition and is fixed to an ejectable sub-assembly placed at the rear of the munition. The weight of this casing is necessary to withstand the forces due to acceleration and it enables the range of the munition to be increased during the ballistic phase. During the transition from the ballistic phase to the guided phase, the ejectable sub-assembly is ejected, taking with it the casing which thus frees the airfoil surfaces to open out. The casing thus positioned also provides sealing and protection of the sensitive parts and rigidity of the whole of the munition.