I happened to see the start of Magnum PI this afternoon. In the opening sequence Magnum loads a 1911 pistol. The magazine apperared to me to be a .38S or 9mm type. The mag looked like it had a line in front of the witness holes.
I have heard that the .45APC round was difficult to make the gun run using blanks. Seems to me that a higher energy .38S blank could move the slide for semiauto stage shooting.