Mark
Good post mate , and a lot of answers will be coming your way
I think only you can answer that
Put some targets out at 60 yards and see how close you get to the bull
The rifle has the power to drop stone dead pigeon/ rabbits at that range , weather conditions allowing i.e. Wind
Would be the maim factor, and a clear shot
And right or wrong I have took the shot at 60 yards , and a clean kill was the end result , head shot only tho
Your mill dots won't come into it to much as you can zero out to really to 40 yards if you want to
That's my zero range with .177
To answer your