Small-, medium-, and large-caliber combustible cartridge cases and propellant combustible containers that are manufactured using reactive injection molding of azido polymers. An injection process for a single propellant combustible charge including the steps of: providing a quantity of azido bearing polymer; providing a quantity of curing agent; optionally providing a quantity of chemical blowing agent; optionally providing a quantity of fibers; optionally providing a quantity of additives and catalysts; and providing a mold defining a male cavity, a female cavity, and an injection port. The injection process further includes mixing together the azido bearing polymer, the curing agent, the optional chemical blowing agent, the optional fibers, the optional additives and catalysts, and injecting the resulting mixture into the mold.