A method is described for producing fibre-reinforced plastic moulded parts, wherein endless fibre strands are fed by a fibre braking device and/or cut fibres via a gravimetric metering device, and a plastic material to be melted, by a volumetric metering device are fed to a single-screw plasticizing unit. Plastic material which is molten and is mixed with fibre material is injected into a moulding tool by an injection stroke of the plasticizing screw. According to the application, the ACTUAL mass flow of the plastic material is calculated from the ACTUAL volume flow of the plastic material and from the ACTUAL mass flow of the fibre material. The ACTUAL mass flow of the plastic material is compared to a TARGET mass flow of the plastic material, and the rotation speed nd of the rotary drive of the metering element of the metering device is adapted.