WOW! Lots of guys reading too many magazines!
Which one are you getting your information from?
The primary change to the 'A-2' was for the 3 shot burst so barrel overheating wasn't a problem like it was on the A-1.
From the USMC Firepower Division, Quantico Virginia M16A1E1 Test Results and Final Report dated 21 May 1980 as published in
The Black Rifle by R Blake Stevens and Edward C Ezell, Collector Grade Publications 1987 pp348 under Advantages:
Increased ammunition conservation and more effective use of ammunition with [3-round] burst control device.
There is no mention of barrels overheating being a problem with the M16A1.
Looking through all of my references on the M16 I can find no official report of barrel overheating being a problem. I have used this system for a living as both a US Army Infantryman and a police officer for 35 years and I have quite a library on it. The original barrel was prone to bending but not because of heat but because Soldiers and Marines treat the rough, use them as field expedient pry bars and otherwise misuse them.....
Most of the A-2 Aperture leaves were either a large, open hole that was intended for NIGHT SIGHTS & CQB...
And the smaller hole was intended for actually AIMING the weapon beyond 50 meters.
Wrong again. From TM9-1005-319-10 Operator's Manual For Rifle, 5.56mm, M16A2 W/E, Rifle, 5.56mm, M16A3, Rifle 5.56mm M16A4, Carbine 5.56, M4 W/E, Carbine, 5.56mm M4A1 published by the Department of the Army October 1998 pp 0011-00-1
ADJUSTABLE REAR SIGHT - TWO APERTURES FOR RANGE
SHORT RANGE OR AT NIGHT-This larger aperture is used for 0-200 meters range. As shown the sight is set for 0-200 meters. This larger aperture is only used when the rear sight is all the way down. In other words the 300-meter mark is aligned with the mark on the left side of the receiver. Useful for moving targets.
NORMAL RANGE- The aperture is unmarked and used for most firing situations. It is used in conjunction with the elevation knob for 300, 400, 500, 600, 700, and 800-meter targets.
In 'Operational' situations, We used to drill one out for night/CQB operations, but for the most part the National Match version of rear sight was MUCH MORE ACCURATE than the A-2 version was.
What operational situations were those? What unit commander authorized the replacement of standard sights with NM sights on MTOE weapons?
The A-2 also saw the advent of the 'bump' so left handed shooters didn't wind up with hot brass in their collars!
There was a little piece of plastic and metal called a left hand firing adapter that was developed and produced to fix this problem on the M6A1.
I saw how the 'Internet Experts' foamed at the mouth, so maybe I shouldn't mention the change in the number of detents in the front sight or the switch from taper pins to roll pins holding the front sight/gas block on...?
No, why don't you tell us about it? Enquiring minds want to know....Taper pins are still the standard on military rifles. No such change was ever made.
If I say anything about the firing pin detent pin change
That's odd, Neither TM9-1005-249-23&P (M16A1) nor TM9-1005-319-23&P (M16A2, A3, A4, M4, M4A1) lists anything called a firing pin detent pin. Could it be you are referring to a firing pin
retaining pin? Surely someone with so much experience with the weapon wouldn't make a mistake like that?
The firing pin retaining pin hasn't been changed since 1967 when it was changed from a machined pin to the less expensive cotter pin design currently in use.
Thank you Mr. White. 
