An injector (100) for a molten metal supply system includes an injector housing (102) configured to contain molten metal. A molten metal supply source (132) is in fluid communication with the housing (102). A piston (104) extends into the housing (102). The piston (102) is movable through a return stroke allowing molten metal (134) to be received into the housing (102) from the molten metal supply source (132), and a displacement stroke for displacing the molten metal (134) from the housing (102). A gas supply source (144) is in fluid communication with the housing (102) through a gas control valve (146). The gas supply source (144) is used to pressurize a space (148) formed between the molten metal (134) and the piston (104) during the return stroke of the piston (104) such that when the piston (104) moves through the displacement stroke a compressed gas filled space is formed.
