A barrel assembly for a weapon, said barrel assembly including a barrel; a plurality of projectile assemblies axially disposed in end to end abutting relationship within said barrel for operative sealing engagement with the bore of the barrel, each projectile including a projectile head and an integral cylindrical spacer portion extending axially and rearwardly from said projectile head; discrete propellant charges accommodated within said cylindrical spacer portion for propelling respective projectile assemblies sequentially through the muzzle of the barrel; ignition means for igniting said discrete propellant charges; and control means for selectively and sequentially actuating the ignition means. In one form, each projectile assembly further includes an internal wedging surface, at or adjacent the trailing end of said cylindrical extension which accommodates a tapered nose part of a following projectile, for expanding said trailing end into enhanced sealing engagement with the barrel upon engagement of said wedging surface with said tapered nose part.