From the A7 take the A369 north (sign-posted to Ronda and Jimena) at exit 115km.  Keep going on this road until you reach Estacion de Jimena.  Drive through the village of Estacion de Jimena and turn left at first sign to Jimena de la Frontera. Go up the tree lined road until you get to a supermarket on the left-hand side (Ruiz Galan) and a restaurant on the right (La Cuenca). Turn left and follow the road round until you get to the bottom. You have a choice of left over the bridge or right. Turn right and then almost immediately left down the track marked 'Real Fabrica de Artilleria de Carlos III'.  Follow this track, which bends first left and then right, past the yellow house, along the high wall to the stone house on corner. By the stone house turn right and follow the track round to the large brown electronic gates.  La Fabrica de Bombas is through these gates.