Unfortunately, talking with someone who works (or worked) at S&W in some technical capacity is about the only way to answer such metallurgical questions - assuming he would talk. I am unaware that S&W gave more than casual mention about model-by-model details about steel alloys used and heat treating methods. It has been mentioned that different alloys and heat treatment methods were employed in the development of .357 and .44 Magnum revolvers. A competent metallurgist could probably perform testing to determine the alloys used and heat treatment performed if you gave him a gun to work with. But you wouldn't want the gun after he finished with it.