I don't know about "the most accurate load" in other manuals, but Lyman made this decision based on which load gave the lowest standarddeviation in velocity as measured by their chronograph. This is very misleading, because the MOST ACCURATE LOAD IN A GIVEN GUN WILL OFTENBE ONE IN WHICH THE STANDARD DEVIATION IN MV IS FAR FROM BEING THE LOWEST! IMO, "the most accurate load should be the one that shoots the smallest groups.

In addition, what shot best in the gun used by the load developer might not do the same (probably won't!!) in YOUR RIFLE. However, this load might prove to be a good starting point for you to use to develop your own "most accurate load". Your best load may be above or below the one in the book.