I have both 1/9 factory & 1/8 custom 264 barrels. Shooting Sierra 140 GK, Hornady 140 or 143, Nosler 140 AB, makes no difference, excellent accuracy with all. I have other 6.5's both with 1/9 & 18 twist that shoot very accurately with all the 140 class bullets i use. Been shooting the 264 since 1964 with a great many Sierra 140's & accuracy has always been great.. Have not tried 156gr bullets & have no plan to try them.
