The reason is that there are huge numbers of errors in it. He wouldn't even correct problems that the documentation was sent to him about. For instance, the RI/3 marked M1A1stocks are post WWII according to him. But he was given the info that the stocks are WWII production made by J. S. Richardson Inc. But he refused to change it in his last edition believing HE was right and nobody was going to change his mind! I hate to speak ill of the dead, but that attitude and his refusal to correct mistakes with documented info is why we disparage the contents of the book. Aside from that, all carbines are transitional. There is no such thing as model of such and such a year. It would take a whole new book just to list the errors.