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.