The study discusses the thermo-mechanical stress distribution in the plunger of a cold chamber casting machine with a horizontal casting chamber in the stationary aspect. The main stresses as well as the reduced stresses were determined for four different strength hypotheses, two of which took into account different acceptable maximal tensile and compressive stresses. For comparative purposes, the calculations were performed for three different construction materials used for cold chamber pressure machine plungers: grey pearlitic cast iron, high silicon bronze and beryllium bronze, as well as one more type of bronze, which has not been used for plungers so far, i.e. aluminium-iron-nickel bronze, constituting the initial alloy for the newly-developed complex bronzes with high wear resistance and elevated strength.