I've read much of the information contributed to this web site in the past year, as well as articles from the links, including the Maryland Shooters site.
The consensus on "optimum" barrel length for a "serious" AR15 has been the 16" barrel. Short enough for CQB but long enough to "reach out there".
Now, the reports from the Afghan sandbox include "suggestions" of lack of knockdown power from the 16" M16's; something not reported from our soldiers with the 20" rifles.
Are we changing our thinking as a result of this information?
Are there any studies measuring M855 energy out of 16" and 20" tubes at varying distances?
I don't recall any short-barrelled ARs on the line at Camp Perry in past years.
If the flag every goes up, I would prefer to be able to "reach out and touch someone" rather than waiting until I "can see the whites of their eyes".