There are two images from xv century manuscripts which make us to think that some ramrods were made from iron. This image are from manuscript of Edward IV and image from Berner Chronik of 1483. The first detail which indicate the material of ramrods is the color. The second details is the thin hook in the tip of the one of this ramrods. It is impossible to make this hook from wood. Such thin hook surely would be broken if it were made of wood. So i think that it was made of iron. By the way I think that hook was needed for hanging to belt in time of shooting or hanging to nail in the arsenal room.
Else we have interesting inventor of Lille 1458 year:
"...100 autres couleuvrines de bronze, aussi avec manches en bois, ayant clef comme arbalète, accompagnées de 99 torcays (carquois), pourvu chacun d'un bluchotois (petite mesure)en fer blanc pour doser la charge de poudre, d'un moule en pierre blanche pour fondre les plommets et d'une estampe de fer (chargeoir) pour mettre la poudre..."
I think that "estampe de fer" may be a iron ramrod. But it's only assumption. We can't say exactly...