The books mentioned are just a yardstick to use in evaluating a particular rifle. With over 70 years having passed since the M1s first inception, there are too many variables to consider when evaluating any given rifle. I wouldn't go "hog wild" and change out parts willy nilly without evaluating the rifle to see, first, if the parts currently in place are actually correct. Scott Duff indicated in one of his books, that if the part "appears" to be incorrect; might actually, be correct.