Those stocks are NOT
older than the gun. They are, in fact, quite a bit newer. The checkering pattern is postwar and the shoulder indicates they are no earlier than about 1953. The prewar Magna stocks had a greater degree of coverage by the checkering and they had a sharp shoulder. Here are some pictures of the prewar style Magna stocks:
Exterior, showing the checkering and the sharp shoulder.
Inside, showing the machined steel retaining washer.