I'm guessing that you want to print the part and produce a plaster or sand cast around it to pour the molten metal into, as it wouldn't be possible to print a plastic mold that would withstand the temperatures for metal casting. In that case, the precision and surface quality is as much determined by the print (slicer) settings as the filament. Something easy to print such as standard PLA or ABS with slicer settings of < 0.15 mm layer thickness, optimum print temp to give a clean extrusion with no stringing, and a good quality filament with high tolerance on diameter and ovality should be fine. You could even do some post processing of the print to get really smooth surfaces (though this can involve some nasty chemicals).
apologies if the answer came too late to help!