Before to many feathers get ruffled or puffed out
The question the OP was asking was bascially does a '06 have enough energy? Not should I take my 06 or 416 Rigby "WATER BUFFALO" hunting. It was just a basic energy question. And as I, Mr. Allen and others stated , yes. But a BIG BUT. Besause if you miss sticking it in the ear or spine nope, not going to fall over drt.
Now, the basis of the OP's Question came from the second installment of the Snipers program ran on History Channel this past weekend. If you didn't catch it the sniper shot a W.buff at like 700 plus. it fell over dead exposing 2 Viet Cong carrying AK's. He then killed them both as they stood there beside a dead, maimed, or otherwise unable to stand and plow fields W.Buff.
No LR water buff hunting planned, I don't believe. Just a simple energy and could it be done question.
Gene
Kirby hit the nail on the head with the statement that it is all about penetration and shot placement, however; with the caveat that the projectile is designed to penetrate, in a straight line (non spire pointed, preferably a fat radiused meplat) and fired from a cartridge with enough retained velocity to facilitate this penetration.
With that lets look at some facts about this cartridge, penetration and composition of a asiatic buffalo. The Australian water buffalo is roughly 36-42"+ in width across the widest part of the chest. A broad side shot needs to penetrate through BOTH lungs for a reliable kill. I have recovered an absessed .458 bullet from the lung of a Cape Buffalo. A wound that penetrated one lung and had scarred up and healed up around the bullet, with the buffalo living only to be shot by myself years later. With this we need penetration of over 30" to reliably penetrate both lungs. These large animals can easily live for days and ultimately survive indefinately with the deflation of one lung. This does not account for hitting heavy bone on the way in. Other killing shots would be of course CNS or major circulatory system interruption. For the sake of this argument let us look at a lung shot as the largest vital area.
Mike LaGrange former Zimbabwean game ranger and elephant control officer with over 4000 elephants killed by himself during his tenure, wrote a book titled "Ballistics in Perspective" wherein he conducted experiments on penetration of all popular standard sporting cartridges up to the largest dangerous game cartridges.
The 30-06 with the highest sectional density bullets of 220 g. Steel core copper jacketed "solids" we're fired from a distance of 30 feet at a muzzle velocity of 2420 fps, into a media used to simulate the thick skinned, hydrostatic shock, absorbing properties of buffalo and elephant flesh, sans impact with heavy bone. The 30-06 averaged a penetration depth of 39".
39 inces of straight line penetration at a distance of 30 feet. So now we take a 38" deep buffalo at 1500 feet, 50 times the distance of the simulated penetration test and a penetration depth of 30"+ is needed. it just does not seem too favorable that any shot that encounters moving muscles, bone etc...would have but the most remote chance of adequately penetrating to the depth needed to reliably damage, to the point of quick death, the vital organs of a buffalo.
Of course this is theory and simulated penetration tests. However tests conducted by a group of men who amongst them have killed over 10,000 of the largest living creatures on earth (elephants) with a more varied assortment of rifles and projectiles than many of us have ever had the opportunity to shoot. I myself have fired over 35, 570g 500 Nitro Express solids into buffalo, elephant and hippo at ranges never to exceed 50 yards and have NEVER had a bullet exit on any of these animals.
So is it possible to pull off this 500 yark buffalo kill shot with a 30-06? Of course anything is possible. Is it realistic? I would say unaquivically NO. Maybe it's time to call Mythbusters!
Hope some find this info useful.