Original mags did not drop free (intentionally, lot of armies prefer this in case the mag release gets bumped, it's why Germany went from the Luger's 1911-style button to the P38's heel catch) from what I remember, the half moon is to help strip the mag out of the gun.
"And Shepherds we shall be. For thee, my Lord for thee. Power hath descended forth from thy hand, that our feet may swiftly carry out thy command. So we shall flow a river forth to thee and teeming with souls shall it ever be. In nomine Patris, et fili, et Spiritus Sancti. Amen."