Bobin, IIRC he stated either 7 1/2" (7.5) or 7.87, seems I have seen both for Military rifles stated, Suffice to say, back when the book 'Handloading for Hunters' was published.
It was LONG ago, and it was mostly military Swedish Mausers and perhaps a few Husqvarna's (not 94/96 mil-surp) and Parker Hale rifles around, but 7.5-8 has often been a typical twist used in 6.5x55s.
