Exemplary embodiments of the invention provide a casting apparatus for continuously casting a metal strip article (e.g. a twin-belt metal caster or a twin-block metal caster). The apparatus has a casting cavity defined between a pair of moving elongated opposed casting surfaces, and the casting cavity has an entrance and an exit aligned in a direction of casting. The casting cavity is also provided with a molten metal injector at its entrance, the injector having an internal metal channel including a downstream opening for introducing molten metal into the casting cavity, and a pair of side dams at each lateral side of the casting cavity for confining molten metal from the injector within the cavity. At least one of the side dams comprises an elongated element that is movable laterally relative to the direction of casting during a casting operation. The elongated element extends in the direction of casting from the injector longitudinally between the casting surfaces at least to a downstream position within the casting cavity where the metal adjacent the element is laterally self-supporting.