Abstract: A capsule is configured to have the outward appearance of a cartridge for a firearm and the capsule is designed to explode within a chamber of a firearm and disable the firearm when fired from the firearm. The capsule includes a casing; a bullet shaped container; a high explosive and a primer. The casing is made to fit within a firing chamber of the firearm. A bullet-shaped container holds a high explosive and fits within the casing to give an outward appearance of an ordinary bullet in a regular cartridge for that firearm. The primer is accessible to a firing pin of the firearm acting on the casing. The primer includes a small charge of a mixture in contact with the high explosive such that when the primer is struck by the firing pin of the firearm, the primer causes the high explosive to detonate disabling the firearm.