"Why is it only that on everyone of these, "whats the lightest" threads(which are nearly a daily thing now), I NEVER see anyone posting about the animals that ran off with an arrow in them, never to be found, because of insufficient penetration? I KNOW it happens, I've seen it happen, I've had it happen to myself, back when I started hunting with a 45# bow. I've spent DAYS of hunting time helping others track animals that they didn't get enough penetration on. I've found dead deer in the woods with arrows in them that didn't go in far enough. I've read articles where I knew that the writer didn't get enough penetration on the animal in question, but that was never mentioned."
That is a VERY easy question to answer. Simply put, becuase those very things you mention happen with EVERY bow weight, from 40 to 90 pounds. It takes very little energy to push an arrow through the rib cage of most animals, unless you're talking water buffalo or some other huge ribbed animals that the vast majority of us are never likely to hunt anyway. Simply put, if you hit a deer in the rib cage, unless your arrow is flying so poorly that it can't possibly penetrate, it matters not whether the deer is 90 lbs or 290 lbs.
Some people never like the facts to get in the way of a good story but 99% of the animals that are not recovered are for one of two reasons. (or a combination of both)
1. They were hit in the wrong spot, regardless of draw weight.
2. They were indeed hit fatally but just couldn't be found.
KPC