Image Number 4 for United States Patent #8573127.
A high velocity cartridge munition comprises a cartridge shell and a projectile inserted into it. A propulsion chamber within the cartridge shell receives a propulsive charge that may be ignited by a pyrotechnic igniter and that develops propulsive gases that act on the base of the projectile, driving it out of the cartridge shell. To prevent the pyrotechnic igniter from igniting spontaneously, and from igniting the propulsive charge due to the ambient temperature or because of a fire, which would cause the cartridge shell and projectile to be separated and fly apart, at least one exhaust channel between the propulsion chamber and the exterior of the cartridge shell is filled with a fusible material. The fusible material has a lower melting point than the ignition point of the igniter and of the propulsive charge. If the ambient temperature of the cartridge shell rises above the melting point of the fusible material, it melts, releasing the exhaust channels, so that, upon delayed ignition of the propulsive charge, it burns without pressure buildup, and the cartridge shell and projectile remain together. At least one non-fusible, rupturable member is positioned between the fusible material and the propulsive charge to provide mechanical support under normal conditions but to facilitate release of gases if the propulsive charge ignites.