Hornady now has a .268", 160gr. RN, by the way, listed as a 'Carcano' bullet.

If you have a .268" groove diameter, this oversized Hornady 160gr. might be 'better' than the .264/.263" commonly available bullets.

If your oversized 6.5 is like my oversized 9.3 - maybe it won't care, accuracy wise about shooting undersized bullets. The 9.3x57 is actually .370" groove to groove and still shoots an inch at 100 meters with .365" through .367" bullets.