How far are confident to shoot

I have just got back from a hunting trip, 4 rabbits at different ranges from sub 50m to 79.6m. 

I use a. 177 running at 830 fps with 15gr slugs. At these distances it's normal for me to take the shot, I rarely miss given good conditions. 

I love. 177, many would say its too far to shoot at these distances. Time and practice and knowing your guns and your own capabilities, and confidence.

I guess you still have conscription, I volunteered, (UK) you are taught to know your weapon inside out.

How far is too far to shoot live quarry, do you take the odd shot that you aren't 100% sure of.

A. Clean kill is what I aim for but sh1t happens, so just occasionaly a second shot is required but rarely. 
 
I would say that if you can hold your groups to the size of a kill shot for the animal and your FPE is still at an acceptable level, at that range, take the shot. That is if you are good with the wind as it makes a huge difference.

I would not take the shot unless I was 99% sure it would be good. At least these will be my parameters when I start pesting.
 
assuming its ~900fps, on small stuff where it needs to be held within 1.5" or so im only real 'confident' to about 45 but this is usually offhand, brace it on a tree type shots .. larger stuff i can take it to 70 or so .. yeah i have 'kill areas' i have pre-sighted in my yard that are further i know i can hit everytime but offhand in the field i like to keep it in the point blank range ... another weak spot i got is 'really close' .. yeah snake on the ground 10ft away, forget it lol .. i'd rather back off to 20y to snipe him ...
 
Went ground squirrel hunting yesterday for a couple hours on a friend's avocado property. Nailed 6 of 'em. 1st one at 76 yards, all the rest between 92 & 116 yards. I'm REALLY confident of my equipment (FX Boss) & getting more & more confidence in MY abilities. A little over a year ago I might have passed on the 90+ shots. Practice & time does wonders for personal confidence. They were all kill shots but was less than thrilled with a couple shot placements only due to the fact that I was shooting across a small canyon with some squirrely (pardon the pun) winds blowing. Time for more practice with wind & in time the confidence will come. 
 
Truthfully,I get more thrill out of stocking than shooting long distances,they are different ,but should have the same results.

I think 60 yds. with a pellet rifle is my max if I could not get closer,it becomes a game=stocking....of course hitting you target with a kill shot at a long distance knowing it is a kill shot is another type of thrill....Oh No! I used the word thrill,sorry "The Thrill is Gone" B B King