So why might a .41 Magnum been used, instead of the .44? The truth is that, previous to all of the hype generated by the Dirty Harry movies, the M-29, was just plain not popular. The gun was (and continues to be) big, heavy, unpleasant to shoot, and overpowered for defense. It's only real use would be for hunting larger animals, and hunting with a handgun was almost unheard of back in the fifties, and sixties. The Model 29 was always a gun of very limited numbers, bought by a small and specialized segment of the shooting public. At the time that Dirty Harry was being produced, the Model 29 was not even being made. Clint Eastwood has never commented on these rumors, and may not have known himself, what he was firing, so closely do these guns resemble each other. Movie guns are generally specially modified so that real ammunition can not chamber or fire in them, making the distinction between these, very similar guns, even more difficult to determine. Studio armourers handle all firearms, and all blank ammunition. What is known, is that Clint procured an actual .44 so that he could get a feel for what shooting the gun was like, to help him better play his part. The gun he used, is said to have been made up specially from extra parts, and repair spares that were stocked by the factory.