A sealing ring obturates a propellant charge cartridge of an automatic firearm for caseless ammunition, in particular against an end face of a firearm element, in particular for a breech or a projectile cartridge. The sealing ring contains a sealing surface that can be brought into contact with the end face. The sealing surface contains a first region around an annular opening of the sealing ring and a second region around the first region. The second region is set back relative to a tangential surface to the first region. In addition, a propellant charge cartridge for an automatic firearm for caseless ammunition, has at least one of the sealing rings. The propellant charge cartridge preferably contains one or multiple, in particular two, propellant charge chambers, which are provided with a sealing ring on each of the breech side and the projectile cartridge side.