to answer the question , yes it will drop in , albeit very loosely , but indeed it will be a bad experience should it be fired , i think it too long to allow the revolution of the cylinder and actuating of the fire control group but ... i never say never or always with enfeilds ...i will say DO NOT DO THIS ,

all that said , nice example of a mkI , shame you had to part with a fine example of a mkI** to get it , you really need both in your collection ,