I took the Remington LTR 223 out to 844 yards today. I wasn't doing so great at that range with 1/5, so I backed it down to 545 and shot a mediocre group with a lot of vertical.
I ended up going prone and that is when I noticed the eyepiece had gotten loose. I locked it down, made sure I had all my fundamentals in order, and proceeded to go 5/5 on the 5" plate at 545.
It is the middle target in this pic