Subsonic firearm cartridge

A firearm cartridge case, comprising:

• a head section;
• a body section, adjacent to the head section;
• a shoulder section, adjacent to the body section;
• and
• a neck section, adjacent to the shoulder section,
• wherein the firearm cartridge case includes a case wall, the case wall defining a chamber that extends from the head section to the neck section and having at least a first thickness about the body section and a second thickness about the shoulder section,
• wherein the second thickness is less than the first thickness, and
• wherein the body section has a first inside diameter, the neck section has a second inside diameter, and the shoulder section has a third inside diameter, wherein the third inside diameter is greater than the first inside diameter and the second inside diameter.

A method for manufacturing a firearm cartridge, comprising:

• providing a cartridge case, wherein the cartridge case comprises:
• a head section;
• a body section, adjacent to the head section;
• a shoulder section, adjacent to the body section;
• and
• a neck section, adjacent to the shoulder section,
• wherein the cartridge case includes a case wall, the case wall defining a chamber that extends from the head section to the neck section and having at least a first thickness about the body section,
• removing a portion of the case wall from within the chamber such that the case wall about the shoulder section defines a hollow volume and has a second thickness that is less than the first thickness;
• loading a predetermined amount of a propellant into the first chamber portion;
• inserting a projectile into the chamber to a predetermined distance from the head section such that an engagement is formed between at least the neck section and the projectile;
• and
• crimping the case wall about the neck section such that a seal separating the chamber from an external environment is formed by the projectile and the case wall.