Stretched it back out yesterday evening (171 yards this time).
This is after the mirror trick, and the shooting close trick, and the plumb bomb trick, and the etc etc etc trick. Readjusted the bubble level on the gun so that I know when the bubble level is good, my vertical crosshair is truly vertical.
So, first shot @ 171 drifted right again, off the paper. Maybe 12-15inches? and only basing that on the fact that it hit that woven wire fence (like it did the first attempt at 170+ a few weeks ago) and threw some shrapnel back into my cardboard. I did see the woven wire vibrate when hit, but hard to pinpoint exactly where hit. Adjusted it to the left so that I could shoot my groups. Wind was pretty dang minimal. Very slight headwind, and only on some of the shots. I'd guess most shots were no wind, but I could feel a gentle push straight in from the target on some of the shots, couldn't have been more than 2-3mph at it's peak, and it wasn't peaking very often.
I think spin drift.