Firstly and most importantly, the Marksmanship Unit at Quantico had little to nothing to do with the development or final design features of the M16A2. Contrary to what appears in some modern Marine Corps History Books, we infantry offices that ran the program knew enough about range and re-qual shooting to consider this in considering changes; while maintaining a "feature balance" and not screwing up a great assalt rifle. (Note: one of these officers (Majors) was/is now BGEN John Sattler, Commanding General 2nd Marine Division--just in case someone wants to confirm any of this) In fact, the only issue they (the bely shooters) had (and lost) was making the barrel heavy throughout. But this was really just one guy (Major Bruce "old dad" Winchensen) who actually worked for the same LtCol Dick Moresco at the Firepower Division of Quantico's Development Center (these days called PM Ground Weapons, MarCorSysCom).
Bruce was assigned to run the Operational Testing, some of which was hosted by the Marksmanship Unit, but the troops were grunts from 2ndDiv and a Squad from Ft. Benning.
Bottom line is that the "changes" came from my side of the equation as I dug most of these out of the woodwork at Picatinny Arsenal and Colt in Hartford. For example, the basis for the A2 rear sight was from a relic LMG Colt had forgotten about from the 70's that I found in their gun room, and one of their guys (Rob Roy) carried it (upper receiver) through Colt's Security under a coat one afternoon so I could take it back to Picatinny for evaluation and modification.
Part of my job was not just coming up with the changes needed, but ensuring we were not making mistakes. So I was touching base with all concerned, including the Army's Human Engineering Lab at Aberdeen Maryland. There was a fellow there (Paul Ellis) who had a book of human (95% centile) human size parameters. I remember one illustraion of how far/close the shooter's eye needed to be from the rear sight, ideal length of pull etc.
Well the "ideal for the 95% Soldier stock length using a rear mounted peep sight was a full one-inch longer than an M16A1. So making the stock better fit American size humans was put on the list. However, it ended up being limited to 5/8" because that allowed the A2 to fit in the many thousands of standard armory M12 Rifle Racks, and not adversely increasing life cycle cost was one of many overiding factors meant to control my enthusiam for change that had been imposed on me by my boss, LtCol Moresco.
ColdBlue sends...