I am told the new model is almost flat in the center where as the old model is supposed to be raised where the pin slides thru the cylinder, So I am not sure about the file work on the cylinder needed to fit a new model cylinder to an old model frame. And if not filing on the cylinder then I don't think the other cylinder would fit the frame. On my 22 , 357, 44, and the 45 all three screws and all have the flat frame and raised hub center section so I am a bit confused on what to file.