Abstract: The invention relates to an artillery projectile with spreading tail assembly and a synchronization ring for controlling the orientation of the fins of the tail assembly. The synchronization ring slides on an extension of the projectile base and includes a first means cooperating with at least one piston seated in the projectile base to hold the synchronization ring in the forward position on the one hand, and on the other hand a second means cooperating with a projection of the respective fins to hold the fins in folded position inside the launcher tube when the synchronization ring is held in the forward position. The fins are spread when the ring moves to its rearward position. The movement of the ring may be under the control of one or more of the launching pressure at the projectile base, inertia, a specially generated pressure, rotational forces, or combinations of these.