An injector for a molten metal supply system includes an injector housing configured to contain molten metal. A molten metal supply source is in fluid communication with the housing. A piston extends into the housing. The piston is movable through a return stroke allowing molten metal to be received into the housing from the molten metal supply source, and a displacement stroke for displacing the molten metal from the housing. A gas supply source is in fluid communication with the housing through a gas control valve. The gas supply source is used to pressurize a space formed between the molten metal and the piston during the return stroke of the piston such that when the piston moves through the displacement stroke a compressed gas filled space is formed.
