Interesting topic on many levels. Pardon my ramble, but a few thoughts bubble to the surface.
There has been a great focus by modern shooters on FPE and MV as a litmus for effectiveness for application of various arms and for many years I was in the same camp. Oh sure, I was aware of the sometimes debate but it has never quite been resolved. A personal experience ongoing since around 2004 has firmly convinced me that both are a foolish benchmark at best.
It was back then that I began, quite without expecting to do so, killing hogs with a SS .22 rifle. Not just any rifle, but one chambered for shorts, supplied with a large quantity of CCI CB shorts and so equipped demonstrated MOA accuracy to 50 yards consistently. Over the years it has accounted for about 100 hogs, all dead by a single shot save for 2 which required a second pop. Necropsy revealed an equally consistent pattern of performance. Complete penetration of the neck and cervical vertebrae on hogs up to about 125#, or full penetration of the skull from frontal shots regardless of size. While fully recognizing that a shot to the boiler room wasn't going to precipitate immediate immobilization, I have no doubt that in time they would have been fatal with reasonable placement. I loathe climbing trees.
Somewhere along the way I have read a variety of discussions about the effectiveness of various bore rifles on big game and despite the telling by Taylor, Bell and other legends I would not think the issue quiet by any measure. There is, or was great controversy about the merits of the 8 bore vs. 4 bore and probably every other bore/caliber that ever was. Methinks it might fall back to placement for the most part, but that's just the way my mind works.
An interesting read that is not the least casual for those interested in terminal ballistics:
http://www.rathcoombe.net/sci-tech/ballistics/wounding.htmlPrimarily focused on wounding theory as relates to conical bullets, it does nonetheless infer clearly why larger bores/calibers of old are not as feeble as many current generation hunters seem to think. The fallacy lies in what causes death, not the measure of an abstract physics calculation.
With that said, I came to know a very interesting gunsmith whose predilection for old arms of quality has left him expert qualified in my view. He related a story not long ago after affecting repairs on a very cherished old German built SxS 16 bore, the story being about his experience with an 8 bore English SxS that he charged with BP and ball per the period of its build. The gun is remarkably accurate and very well regulated, placing balls within a very few inches at 100 yards. I mean like 2-3" with no cross over. I don't recall, the load used, but it was substantial. Then he let the cat out of the bag in a manor of speaking.
He said "Dan, I was at the range early on with this gun and it has been a learning experience to say the least. If you ever shoot one of these old guns do not cock both hammers at the same time. Most wouldn't think this a problem, but you really don't want to experience a double with the likes of an 8 bore or larger. I was on the 50 yard line and Steve over there (nodding towards the back of the shop at another employee) was standing behind me off to the side when it doubled on me. One second I was about to shoot and the next my right shoulder, face and left arm were in agony. The gun was gone and Steve was shaking me and asking if I was OK. The sky sort of turned purple there for a spell. The gun was laying on the ground about 10' behind me in the sand."
It's true, some guns can hurt on both ends, but is it FPE, momentum, the Taylor Knockout Formula or just the way it is?