fuzebox, you have the A1 closed bolt, not sure what version, but they all took the same mag. The mag is the same one the Model 80 bolt action uses.
What Lanzerac was saying about the "semi-smokeless" and "smokeless", was critical in the open bolt Mod 50, not so much in the closed bolt. The open bolt had a part you could change inside the receiver to cycle either round. It was the early version of "Standard velocity" and "High velocity" today.