Purchased a used Ruger Mini-30, s/n 189-15XXX, at gunshow this past Sunday. However, after arriving home, suprised to see floorplate on factory (?) five round magazine reads "RUGER mini-14 (logo)". 7.62x39 cartridges fit into mag, and mag pops right into mag well. A pull on the bolt handle seems to properly load a round out of the mag. Are the Mini-14 and Mini-30 magazines interchangeable or could this be (my suspicion) a Mini-30 mag mislabeled with a Mini-14 floorplate ??? Thanks...