A system for use with firearms which permits the ready exchange of barrels on a single action and stock assembly. Depending on the size and energy requirement of the generator, a number of individual excitation modules with a corresponding number of individual excitation windings are provided, wherein a minimum necessary total excitation current can be supplied by superimposing the individual currents of the excitation windings. The compositions can contain at least one anionic surfactant, at least one polyoxyalkylene ammonium cationic surfactant and at least one of an alkaline agent and an acidulating agent. Perpendicular to the bottom is an annular central divider with a sufficiently sharp upper edge for piercing the partition when pressure is applied to the flexible bottom. A thickness of the coating layer is influenced by modifying the surface tension of the coating substance. A method of determining round-trip delay and jitter in an optical network comprises the steps of a) transmitting a test frame over the optical network to a device on the optical network, b) receiving a looped-back test frame from the device over the optical network, and c) determining a round-trip delay measurement using the received looped-back test frame.