Buck Killed With Patched Round Ball

[Renegadehunter]

What would you say the farthest ethical shot would be?

My best answer to this is that most find themselves limited by the accuracy of the load they work up, combined with their own shooting skill, before they worry a whole lot about the "killing power" of a patched RB load. I say it that way because I feel a RB will have the required energy out quite a bit further than most can shoot a group that gives them a warm and fuzzy feeling about trying a shot at a live animal.
A RB will also sometimes for some reason give a really poor blood trail to follow. For that reason I like to hold pretty low in the body cavity, around top of the heart area, so it doesn't take much blood in the chest cavity before it will run out the hole(s).
My own personal choice is to only shoot as far as I can keep all shots within a 4" group. That is different distances depending on my shot options, such as shooting sticks, leaning against a tree, resting an elbow on my knee, freehand, etc.
Now if you have a fabulous load you've worked up combined with a very accurate barrel and good shooting skills so that you can accurately shoot well out past a 100 yards, then there should be charts you can google that will show the energy a specific weight RB has with various powder charges.