Abstract: A method and an apparatus for reducing the spread of hit pattern for a rotationally-stabilized ammunition unit such as a projectile, which is discharged in a ballistic trajectory from an artillery piece towards a target which is to be combated including dynamic balancing of the shell (1) to reduce the effect of the air resistance between different shells, and increase hit probability. The inclination between the main axis of inertia of the shell and the geometric axis of the shell case are measured, whereafter these axes are set in parallel in that an adjustment weight (2) is mounted on one side of the point of gravity of the shell seen in its longitudinal direction. The adjustment weight (2) preferably consists of a disk or washer provided with an eccentric recess (4) for suitable weight and mass eccentricity.

Abstract: The invention relates to means for reducing the spread of shots in a weapon system in which the shots are fired from the weapon in a ballistic trajectory from a launching device towards a target. It comprises means for measuring the position of the target, means for measuring the muzzle velocity of the ammunition unit, and, in one embodiment, also means for measuring the actual trajectory parameters of the ammunition unit (shell, projectile or the like), for instance the reduction of velocity in a specific trajectory distance. In response to these values the impact point is predicted. A braking command is transmitted to the ammunition unit via a radio line in response to the difference between the actual position of the target and the predicted impact point for braking the velocity of the ammunition unit in order to improve the hit probability. The braking means preferably comprises a plurality of braking flaps distributed about the periphery of the ammunition unit.