I think Rockport it the nail on the head with the ethical and unethical discussion.
It's one of those, if you never practice shooting out the 300 yards and then one day see a deer walking at that 300 mark and you decide to take a shot, you are making an unethical decision based on the hopes that it will work out. When you go to the range, practice, practice, and practice and you are comfortable shooting that range and your range time supports this, then you are making an ethical decision supported by your ability and experience.