Coat iron with linseed oil or wax for storage.
I,ve had best results with pewter gray “needle steel”; probably broken up borings from machine shop work. Use commercial “meal D” or equivalent and very thick casings (1″ o.d. Kraft for 3/8″ bore) and press or ram rock hard Clayed ends should be at least 3/8″ thick. Also good for shell tourbillions and serpents.