TL;DR
Do bullets have areas in thier flight path where they destabilize, then re-stabilize and become more accurate?
I have not personally seen this to such a degree in any of my shooting before.
Details:
I've been working on getting a browning a-bolt 7 mag, 1 in 9 twist, sighted in and trajectory mapped. Has a vortex strike eagle 3-18x scope that I pulled off my 308 and has proven rock solid on that.
Heres where it gets wierd. Rifle shoots a hair over moa at 100, 1.5 moa at 200, 2+moa at 300, and .5 to .75 moa at 400. Winds were 5mph and less.
My current life keeps me from having enough time to reload these days, so I'm using factory hornady 162 gr eld-x ammo. Chrono is on perma-loan so I don't know the exact speed of this stuff. Just using hornady data for now.
Not only is it shooting much worse at 300, but it is also shooing much lower at that range than it should. At all other ranges I tested is it right on the money elevation wise when using the hornady app and I was able to get multiple first shot, cold bore hits at 400 and 500 while practicing.
I played around with a bunch of different scenarios assuming my data was off but in no scenario I could come up with does it work out being that far off at 300 and right on everywhere else.
Do bullets have areas of instability that big?