I try to my game shot distance to where I can reliably hit an 8" paper plate at whatever position I may need/be able to take for the shot. If over 300 yards, I'd better have a range finder and a trajectory chart, or won't take the shot. I keep a chart taped to my rifle stock, but have never killed a deer beyond 400 yards. We rarely see them where we hunt in Maine beyond 300 yards. I don't hunt powerline right of ways these days and rarely shot any deer on them, but have spent a lot of time watching for deer there over the years.
I've been shooting offhand for many of my game shots and killed running coyotes with one shot out to 200 yards, which isn't a worlds record, but highly satisfying! Closest I've shot a running deer was about 10 yards, through hardwoods. Lucky that it didn't hit a tree, but well-aimed and one-shot kill. Farthest was 200, across a field and just as it topped a hill, with woods behind it.