A cartridge casing of a cartridge for a lever action firearm, the cartridge casing comprising a rim comprising a flat front face configured to provide a gripping surface for an extractor of the lever action firearm to remove the cartridge casing of the cartridge after firing of the lever action firearm, the rim having a radial gradient that decreases from a maximum radius at a first location on the rim that is prior to the flat front face to a minimum radius value at a second location on the rim corresponding to the flat front face.