Abstract: An armor penetrating round includes an elongated core portion (e.g., a hollow tool steel core) defining a front end, an aft end, and a central cavity which extends from the aft end toward the front end. The central cavity has (i) an aft cross-sectional diameter adjacent the aft end and (ii) a front cross-sectional diameter adjacent the front end, the aft cross-sectional diameter being larger than the front cross-sectional diameter. The armor penetrating round further includes a slug portion (e.g., a pre-compacted pellet of powdered metal) which is disposed within the central cavity adjacent the aft end, and an outer jacket (e.g., a copper jacket) which extends around the elongated core portion to operate as an interface between the armor penetrating round and a gun barrel when the armor penetrating round is fired through the gun barrel.