A fixed round of ammunition for a muzzle loader firearm. The round has a bullet within a sabot that is engaged to a consumable cartridge case. The case is filled with propellant that is precisely calibrated to provide optimal ballistic properties with the particular bullet it is engaged to. The consumable cartridge case can be more tailored to respectively increase or decrease the burn rate of the consumable cartridge case. The consumable cartridge case can be constructed out of nitrocellulose or other energetic materials. A wide range of propellant formulas can be used that are safe because the burn rate is precisely calibrated for the bullet used. The propellant can contain pyrotechnic material and/or other ingredients to reduce the burn rate of a smokeless propellant and can contain a stabilizer to increase the shelf life of the ammunition round.