Parts are diecast from a light metal alloy which in the molten state is fed under gravity into a casting chamber of a diecasting machine and whence forced by a plunger into a mould chamber which undergoes controlled evacuation in accordance with the position of a plunger. A parting compound is applied to at least one mold half and the application of a lubricant to the plunger. The light metal alloy consists of a primary alloy of invariable composition, with a limit placed on the proportions of Cu, Fe and Zn; the alloy undergoes smelting treatment, de-gassing and/or filtration before being introduced. The vacuum in the mould chamber is below 50 mbar when the molten alloy is introduced and the parting compound contains alkali halides and anti-corrosion additives.