Marine PMI and I found ourselves in an interesting situation today. We had no prairiedogs left to shoot and an 18" diameter white rock on a perfect back stop at 695 yards. What made it really interesting was that we both had 6.5's with us: His a Hornady Creedmore and mine the venerable X55 version. Making it even more interesting was that we were both shooting the same bullet: A PPU 120 grain boat tail HP. We'd independently loaded these rounds many months ago with no idea that we'd eventually end up in a shooting match. Both of our loads were doing about 2800 fps with his using H4350 for fuel and mine using IMR 7828SSC. The Marine's rifle is a full blown custom target gun of his build based on a Savage action topped with some decent glass. Mine is the FN Commercial I often speak of topped with a Leupold 3-9X which, for some reason, I never thought to move off of 3X. We each had no zero and only ten rounds. We were both sitting with out guns resting on camera tripods mounted with a small bag; our typical prairiedog set up.
Amazingly, I think we both hit it 4 times, but the interesting thing was that the bullet seemed to require almost no wind correction! We kept on hitting up-wind of the rock due to initial compensation for for the wind. When we held dead on for windage we started getting hits. It may have been that winds of two different directions cancelled each other out but I am doubting it. We were both pleased with our rifles, loads, and especially the bullet. It is very accurate from both of our guns.
So on this occasion there was no difference in performance of these two cartridges. They are pretty much ballistic twins and acted as such today. FWIW...~Muir