Abstract: A firearm cartridge has a case configured with a relatively straight-walled portion and a shoulder portion for housing a quantity of propellant. The case further includes a neck for retaining a bullet. The straight-walled portion defines a base cavity having an interior base diameter. The interior base diameter is approximately twice or more the neck diameter. The diameter ratios of the base and neck optimize combustion efficiency to reduce heat and acceleration losses. The cartridge body cavity is sized and configured to contain a sufficient quantity of propellant such that igniting the propellant causes formation of a propellant plug having a diameter that is approximately the diameter of the bullet, and wherein the propellant plug shears free from unburned propellant that is disposed adjacent the relatively straight-walled body portion.

Abstract: Passive coatings accelerate burning at interfaces between rapidly burning propellants and thermally conductive or endothermic inert surfaces. The coatings, useful in firearm cartridges, firearm chambers, and solid rocket motors, reflect infrared energy from the combustion gases to reduce heat loss to the case or chamber and to accelerate ignition of the propellant. The reflective coating has a thermal breakdown temperature higher than the propellant ignition temperature. Firearm cartridges and chambers may have radial shoulder configuration that focuses a shockwave below a bullet base to reduce heat loss to the bullet and support bullet retention in the neck for a longer period of time.

Abstract: A firearm cartridge has a case configured with a straight-walled portion and a radial shoulder for housing a propellant. The case further includes a neck for retaining a bullet. The straight-walled portion defines a base cavity having an interior base diameter. The interior base diameter is approximately twice or more the neck diameter. The diameter ratios of the base and neck optimize combustion efficiency to reduce heat and acceleration losses. The radial shoulder focuses a shockwave below a bullet base to reduce heat loss to the bullet and support bullet retention in the neck for a longer period of time. A thermally insulating coating is utilized to reduce heat loss to the case or chamber and accelerate ignition of the propellant.