My response is tailored toward hunting and not targets/steel!
It is dependent upon the velocities, BC's, and the zero range! We use a 300 yard zero on our hunting rifles, and easily "hold on hair" out to 400 yards on big game (deer and up). I'm certain the others using high BC bullets and higher velocities can easily stretch that a bit farther!
For hunting purposes, beyond 400 yards....we use the rangefinder and dial!
IMO, the only potential issue with our zero would be shooting small animals (fox, coyote, ect) at the peak of our trajectory (around 170ish yards). You just have to remember to hold a bit low for those shots! Most of the time a non-issue, but, I did manage to shoot over a Rockchuck with my 375 AI by not "thinking" The second shot corrected my mistake.....the Rockchuck was DRT!
memtb