The magazine article and book chapter are one and the same. Jack's book THE HUNTING RIFLE was mostly a collection of previously published OUTDOOR LIFE pieces.
Actually the 4831 mentioned was Hodgdon, specifically the surplus powder so designated. IMR's 4831 didn't appeared until the early 1970's, I believe.
O'Connor liked the 7x57 so much that late in life he used it more than the .270, mostly because it kicked less.
