Abstract: A projectile and sub-projectile assembly including a centering tube positable within a chamber of the projectile to retain the sub-projectile positioned in the projectile. An expandable locking ring is positionable within the projectile through an opening in the rear of the projectile and engageable with a groove. A tube flange cooperates with the tube and the locking ring to maintain the locking ring within the groove and to fix the tube in a centered position substantially coaxial with the projectile. An expulsion piston arrangement is provided including sub-projectile engagement surfaces and sealing elements to seal the chamber from an expulsion charge chamber having an expulsion charge. Upon ignition of the expulsion charge, hot gases act on the piston which acts on the sub-projectile to disengage a base plug from the projectile to allow expulsion of the sub-projectile.