APFSDS Armor-Piercing Fin-Stabilized Discarding Sabot
A tank gun round that discards a lightweight outer sleeve after leaving the barrel, leaving a long, dense metal dart to punch through armor using speed and mass alone, with no explosive warhead involved.
APFSDS is a kinetic-energy tank round: the gun fires a full-caliber sabot casing wrapped around a much narrower penetrator, the sabot falls away within meters of the muzzle, and the surviving dart, stabilized by small fins instead of spin, continues downrange to defeat armor purely through velocity and mass.1 There is no explosive charge in the penetrator itself, which is why it is grouped separately from HEAT and HESH rounds, both of which rely on a shaped-charge or plastic-explosive effect instead of raw kinetic force.2
The round exists because shaped-charge warheads lose effectiveness against sloped and composite armor in ways that pure kinetic penetrators do not, and their performance does not scale simply with a longer gun or higher muzzle velocity. APFSDS performance does scale with velocity and penetrator length-to-diameter ratio, which is why tank gun and ammunition development pushed toward higher-pressure smoothbore guns instead of the rifled barrels used by the round’s predecessor, APDS: a fin-stabilized dart does not need barrel spin to fly straight, so removing the rifling let designers raise chamber pressure and muzzle velocity further. Penetrator material matters too, with tungsten alloy and depleted uranium the two materials in wide service use, trading cost, density and self-sharpening fracture behavior against each other.
What an analyst actually compares between APFSDS rounds is muzzle velocity, penetrator length-to-diameter ratio, and penetrator material, since these three factors determine effective range against a given armor thickness far more than caliber alone does.
WeaponSpecs covers this tradeoff in Tank Armor Explained, and the gun and ammunition fields on the tank type page let you compare which fielded MBTs pair a given main gun with modern APFSDS ammunition versus older stock.
Sources
Related on WeaponSpecs