DMK,
That certainly seems like a reasonable explanation. The problem is that M855 failures and successes are being experience at all ranges. For every credible report of a success that can be provided at a given range, there is someone reporting a failure.
By way of example, I worked with an officer who was a platoon leader with the 10th Mountain Division on 3-4 October 1993. His longest engagement (according to him) was about 25 feet, with the average being about 10 feet. The weapon was an M-16A2. You would think if there was a propensity for the round to have too much velocity he would have experienced it. This directly contrasts to the report AhmugGB posted.
The issue can never be resolved conclusively. Due to the nature of the engagements and the operational environment, detailed analysis, such as that conducted in law enforcement shootings, can not be conducted. As a result, much of the evidence is anecdotal and many of the people sharing their experience have an agenda. (I suppose this applies to my comments as well, though I do not believe I have an agenda.)
The problem, as I see it, is not the theory about velocity/fragmentation. It is the promises of incapacitation it makes. I do not doubt bullets are fragmenting or failing to fragment per the laboratory tests. What I do doubt is fragmentation equals incapacitation and lack of fragmentation equals lack of incapacitation. Suppose a bullet fragments but hits nothing vital at 8 feet? Suppose I hit a guy in the spinal cord at 300 meters? Which one was better.
In my opinion, the people running around talking about velocities and fragmentation are paying too much attention to what the bullet needs to do and not enough attention to what the shooter needs to do.