A subsonic ammunition
cartridge casing having an engineered internal volume designed to allow for the introduction of precisely the amount of
propellant necessary at precisely the desired location to reproducibly produce the desired
projectile velocity and
internal pressure is provided. The subsonic shell casing has an engineered internal
propellant cavity built into the internal body of the casing itself that does not necessarily depend on the introduction of a separate volume reducing device such as tubing, filler, foam filler and the like. This ensures the integrity of the case, does not result in anything being expelled through the
muzzle of the weapon other than the
projectile, does not have any burning or combusting components, allows for very precise control of the internal volume and thus
chamber pressure, and is economical to produce.