Yeah, if this was 55s only, I'd say it was jacket shedding. I had that with a 1x7 Colt AR that I eventually sold off.
But 68s and 77s...those should be running fine,as fast as you can push them.
Absent deep visible jacket scoring, I would say that perhaps you have a scope issue, since you are apparently dialing between 100yds and 200yds, correct?
It's possible that you scope has a weak set of erector springs, and your initial adjustments aren't "taking" for a few shots. This leads to more and more and more adjustments, putting it all over the paper. Any chance this is happening?