A gas operated part forming die apparatus has compact high tonnage presses which are operated by high pressure gas generated within chambers and controlled to operate high pressure pistons and dies for compressing particulate material into dense formed parts. Combustion chambers are filled with pressurized mixtures of combustible gases and diluents. Elongated chambers have insulating walls and spaced electrodes. Some contain liquid or particulate ablatable materials or ablatable liners. Others extend fuzes between the electrodes and are filled with pressurized gases. Gas is removed from the particulate material. Die cavities may be precompressed during filing of chambers with pressurized gas. Igniting the combustible gases or creating arcs between the electrodes produces rapidly expanding high pressure resultant gases for driving pistons and movable dies and rapidly compressing die cavities. Pressures in the chambers are contained, or pistons are restrained until releasing and driving the pistons. Large area pistons drive smaller movable dies.