I posted this on a different sight as well, but I believe that Eastwood meant a special light load, made up for him for use on the street. I seem to recall him saying that in one of the other flicks. I do know that the first gun is a model 29-6 1/2". On Modern Marvels on the History channel, there was a show called "Magnums". In it John Milius is talking in an interview about the guns used during the filming of the Dirty Harry series, and holding the original used in the first film. He said someone- I don't recall who, had presented it to him after the filming was done and the movie was a hit. I believe he also stated that after the change to 6" bbls. in '79 they used that size for the remaining films whenever a 29 was used.