Abstract: An ammunition round for an artillery gun comprises, as an armor piercing nd, an outer tubular disposable sabot and an inner projectile which are joined by interlocking means to join them until exiting from the gun muzzle and separates them in ballistic flight. The interlocking means comprises left-handed threads and right-handed threads; both directions of threads being on both the inner wall of the sabot and the outer wall of the projectile. In one embodiment the two directions of threads are on axially tandem sections and in another embodiment they are on the same section, to form a herringbone pattern with raised diamond-shaped protrusions.