I'm fairly certain that they'd penetrate even the knuckle on a deer at anything less than 20 yards. Like Steve says, he got through both shoulder blades and that was with a 150 grain lighter arrow at 25 lbs lighter draw weight. An 860 grain arrow going 215 fps out of an 80 lb bow is going to be tough to stop, especially with that bone splitting Nanook head. The thing is that these are specifically designed for cape and water buffalo. Nobody is going to be throwing these spears at a deer and even if they were, there's no excuse for trying to kill one with a poor shot. Use reasonable equipment for the job at hand and apply it with good judgement (avoiding poor shots) and there shouldn't be an issue.
Kodiak, I agree with you in saying to avoid poor shots. However, I think we should call it poor shot selection. I'm sure all of us at one point or another in their careers have made the right shot selection, only to execute a poor shot, not hitting exactly where we intended. This is my case for using a head/arrow combination that might help me out a bit with penetration. For the whitetail guys here; My bow is 65lbs with a 28" draw length. My arrows are Gold Tip Pro Hunters with a 100gr Slick Trick weighing in at 375gr. On a good shot, this combo has blown through many deer like a hot knife through butter, no questions asked. On the shot I was referring to earlier, hitting the scapula, it blew through that and all but maybe 8" of the arrow were hanging out the other side. My setup is not heavy at all. Probably more on the mid weight side. But IMO, for whitetails, its plenty. If I were hanging out with Kodiak, you better believe things would get heavier all across the board to hunt game such as moose, brown bear, etc.
