Thread: maximum range

how do you guys determine your maximum hunting range?
I've heard about the 1000ft/lbs rule but what about in terms of accuracy, I'm thinking group size isn't as important but more hitting within a certain distance of point of aim. the kill zone on a deer/tahr must be 10 inches at a guess?
I might just shoot until I get to a point where my wind reading ability fails me, I guess that will be my max range.
I just shot a target off the deck at 640 and my group was just above .5moa with the furtherest poi being about 8 inches away from my point of aim. not to bad considering there was a bit of wind.
be interested to see what others do to determine maximum range