In an ideal world all animals would be compliant and drop instantly with a well placed shot.
Up until last year that was the case with my hunting experiences. Then I managed to draw a moose tag and there he was. Three 200 grain sierra game kings from a .300 win mag at 340 yards and he was down. The first shot took out both lungs and a piece of his heart, the last two were both lung hits.
The moose (not a big moose) managed to stay upright for a full three minutes before he laid down ( of his own accord) and went to sleep. When we tried to find him in the brush we discovered that there was no blood trail whatsoever, luckily we were still able to track him to his final resting place. Two of the bullets were pass throughs, one was resting against the skin on the other side. The exit holes were finger sized and extremely difficult to find as the thick hide, hair and fat had sealed the wound.
IMHO a large exit wound will give an adequate blood trail to follow because as nothing in this world is perfect, odds are eventually you will be tracking an animal (good hit or not).
Here's a pic of the little moose that could! [img]/ubbthreads/images/graemlins/wink.gif[/img]
If you can see there is zero blood outside the aniumal even with two (small) exit wounds.