Reduced energy marking cartridges providing a multi-phase firing cycle

A reduced-energy cartridge having a multi-phase firing cycle comprising:

• a casing having an axial bore including an aft portion extending from a base at a breech end of the cartridge and a fore portion terminating at a muzzle end of the cartridge;
• a sabot telescopically received in the axial bore and coupled to the casing for relative movement from a retracted position to an extended position, wherein the sabot includes a sabot body, a sabot mouth formed at the muzzle end, a blind bore extending axially from the sabot mouth into the sabot body to form an acceleration chamber, and a vent hole extending through the sabot body into the acceleration chamber;
• a first sealing means forming a combustion chamber at the breech end between the casing and the sabot body;
• a second sealing means forming a venting chamber at the muzzle end between the casing and the sabot body;
• a propellant disposed in the aft portion of the casing and ignitable to produce a combustion gas;
• and
• a projectile releasably disposed in the sabot mouth and configured to be propelled from the sabot;
• wherein the multi-phase firing cycle includes:
• a combustion phase, wherein the sabot is positioned in the casing such that the first sealing means is operable for sealing the vent hole from the combustion chamber for pressurizing the combustion chamber with combustion gas for pushing the sabot forward relative to the casing;
• a firing phase, wherein the sabot is position in the casing such that the first sealing means and second sealing means are operable for establishing fluid communication from the combustion chamber into the venting chamber through the vent hole and into the acceleration chamber to propel the projectile from the sabot mouth;
• and
• a venting phase, wherein the sabot is position in the casing such that the first sealing means and second sealing means are operable for establishing fluid communication from the combustion chamber into the venting chamber through the vent hole and the acceleration chamber and out the sabot mouth for expelling combustion gas from the casing through the sabot mouth.

A method for firing a reduced-energy cartridge having a casing, a sabot telescopically received and supported in an axial bore of a casing and for relative axial movement from a retracted position to an extended position, and a projectile releasably disposed in a mouth at a muzzle end of the sabot, the multi-phase firing cycle comprising:

• igniting a propellant in a combustion chamber formed in the casing behind the sabot to generate combustion gas during an ignition phase;
• pressurizing the combustion chamber with combustion gas for sliding the casing relative to the sabot during a combustion phase;
• positioning the sabot in the casing to direct combustion gas from the combustion chamber through a vent hole formed in the sabot and into an acceleration chamber formed in the sabot for propelling the projectile from the mouth of the sabot during a firing phase;
• and
• positioning the sabot in the casing to direct combustion gas from the combustion chamber into a venting chamber through the vent hole and into the acceleration chamber for expelling the combustion gas from the casing.