A cartridge has a case comprising a body housed telescopically within a sleeve. The body encloses a main chamber which contains gas under pressure, and a valve mechanism for venting gas from the chamber into an expansion chamber. The pressure of the gas in the expansion chamber causes the body to move rearwardly relative to the sleeve to apply a force to the breech block of the weapon in which the cartridge is used, thereby to initiate the reloading cycle. Gas is vented from the expansion chamber to eject a projectile when a spigot projecting from the body is withdrawn from an aperture in the end wall of the sleeve.

A compressed gas injection device includes a projectile course for receiving and accelerating projectile bodies, a compressed gas housing which is connected to the projectile course and which is divided up into a compressed gas chamber and a working chamber by a partition. A working piston is arranged in the compressed gas housing and is provided with a valve plate which is arranged on the front end of the piston rod thereof for moveable rear closure of the projectile course, wherein the working piston is a movable backward closure element for the working chamber and the piston rod is guided through the partition.

A cartridge for a firearm includes a cavity at the rear end with an inwardly extending flange. The cartridge includes a cylindrical member having a first end for receiving a bullet and a second end defining a second end wall having an aperture. The second end of the cylindrical member includes a flange portion and defines a cavity with an inwardly extending flange around the circumference of an outer end of the cavity. The flange has an inwardly angled surface which is at an angle sufficient to allow an extractor member, associated with a firearm, to engage the cavity behind the flange.