Originally Posted by AlaskaCub
Originally Posted by Holcombe30347
Originally Posted by AlaskaCub
You know what still has me a bit bamboozled is the fact that the Barnes 168 TTSX loads hit about 1 1/2 to 2" lower than the Fusions do. The 165 gr Coreloks and the 165 grain Interlocks hit to almost the same POI as the Fusions do , and it suprises me that the Barnes loads hit that much lower. Have read that the Fusions are generally loaded a little mild but they have been almost identical to most other 165 gr factory loads I have shot. Cant imagine 3 grains making that much difference or they are just that much slower.
The weight of the boolit has absolutely no bearing on where it will hit the target. Upon firing the barrel vibrates as the boolit is traveling down it, where the boolit exits the barrel in relation to this vibration is where it will impact the target. Thus a lighter boolit can actually hit lower on the target than a heavier one. This is why when we work up loads we search for the one load that exits the barrel in about the middle of the vibration cycle. As you add powder to the load you can see the groups opening and closing because of this phenomenon. Changing something as innocent as the primer can alter POI several inches. It changes the vibrations of the barrel. If you have seen the donuts that Sims sells for the barrel, this is to try and change the harmonics of the barrel. Same goes for the BOSS system on the Browning and Winchester rifles. As you move the BOSS brake out further it changes the harmonics within the barrel.


That makes some sense but it does seem odd that most of the other loads in the same weight grain land very closely to the same POI on a vertical scale and for these 168's to hit even lower than 180 grain Power Points kind of surprised me. This pic below has a group covered in black stickies just below the orange bullseye ,that was 3 shots from factory 180 gr powerpoints and they actually impact higher than the 168 gr TTSX's.

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I had a Tikka 06 once that would shoot 150's 165's and 180's all to the same POI but that was a very unusual barrel. When working up loads I expect the different bullet powder combos to be off by several inches in any direction. Especially the mono boolits like the tsx's. My 6.8 shoots the accubonds and the Sierra prohunters about an inch apart and shoots both very well. If all of this wasn't so. there would be no need for windage adjustments on sighting systems. We would only need up and down elevation adjustments to account for the various weight boolits as the sights would be in the very center of the sighting line and preset at the factory. I love it when a load comes together and when you keep shooting the hole in the target just seems to get a little darker with each shot. Means you have hit the sweet spot for that particular gun/load.