I have to side with elkhuntinguru. I think that bowhunting is totally different than rifle hunting. I think that being able to hit a 6" group with ALL 5-6 arrows is a good determiner of what your maximum distance should be. However, I think it should be in a hunting type situation (not stading flat footed in your back yard in your jeans and tennis shoes next to your 50yd marker, with no wind at noon on saturday) If you can't do this kind of accuracy in hunting clothes, from kneeling/treestand positions while your cold and nervous, you shouldn't attempt the shot.
I know I put a lot of time in my rifle hunting preperation, and KNOW that when I pull the trigger, that the target/animal at the other end of the scope is going to die! I don't think this kind of confidence is possible with a bow.
Some things to consider:
1. Our arrows flight time is MUCH longer than a rifle bullets path. Thus animals have a cance to move postions before the arrow gets there.
2. The sound of the bow is heard well before the arrow gets to the animal which gives them a cance to "jump the string"
3. Wind drift can be quite significant with arrows. It is also difficult to calculate how much drift we will get (lots of practice is the only way).
4. An archers "effective" kill zone is much smaller than a rifle unters. No head, neck, high/front shoulder, no broken leg/hip bones to slow the animal enough for a second shot..... you get the idea. There is no room for error!
I know people that have killed animals at long range with a bow, but these same people have wounded more than their fair share (even if they don't tell others, I bet it is happening).
Now a little background about me so that people reading this know that I do actually know what I am talking about, and not just blowing smoke. I am a registered NFAA Professional. I have been shootin competitively and hunting for 19 years. I have won many 3d and target tournaments at the local, state, and the national level. I travel across the country shooting with the BEST archers in the world, and know what is capable with bow and arrow. I have also worked in the archery industry for years, and see what all types bowhunters are actually capable of when "the chips are down". I have killed 6 elk and 15 deer with archery equipment. Yes I have wounded animals, but that was when I was new and learning. Now, with a strong sense of ethics and hard work, since 1997 I have not wounded/lost a single animal, I missed one mule deer doe in 1999 at 32 yards when my arrow hit a branch I did not see. Everything else that I sent an arrow at has died.
Here are my personal limits and why. Keep in mind that anything over 35 yards MUST be rangefound befre shooting, or I won't take the shot. 2 yards means a LOT with a bow, no matter how fast you are shooting. (I shoot a heavy carbon arrow at 290fps with a good fixed blade broadhead)
Elk: 55 yards max - This in ideal conditions only. They rarely jump the string, and have a large kill zone.
Mule deer: 50 yards - Again ideal conditions only (which is rare in mule deer country) They also don't jump the string very often.
White-tail deer: 35 yards MAX - They are just way to jumpy and hyper and usually move somewhat before the arrow gets there!
Sorry for the long post guys, but I do feel that archery and rifle hunting are different, and long shots at 80+ yards and stuff like that have no place in bowhunting. I think most peolpe that bowhunt enjoy the callenge of getting up close and personal with our prey. So always try and get closer!