Abstract: An electromagnetic rail gun system includes an electromagnetic rail gun, a power supply, a cartridge and breech means for holding the cartridge. The gun includes a breech end and a muzzle end and a pair of substantially parallel rails defining a bore for receiving a projectile. The cartridge has releasably held projectile having a nose and a trailing end carrying an armature. The cartridge also includes a casing comprising a pair of electrically conductive casing segments spaced by insulation. The system further comprises interconnection means from the power supply connecting the breech end of the rails in parallel with the casing segments of a cartridge held in the breech means. The cartridge further includes shunt means interconnecting the casing segments for carrying current therebetween, and the armature is in electrically conductive relationship with the casing segments.