The M16A2 was adopted by the Marines in 1983, and then by the Army three years later, but all of its development was done, largely on a shoestring, by the Marines.
For example, the finger bump on the A2 pistol grip? The very first prototype was built up by a Marine officer on an A1 grip, using plastic wood or body filler! Most of the modifications to the A2 were aimed at:
- Increased practical accuracy;
- Increased effective range;
- Increased durability; and,
- NATO compliance (adopting a NATO round equivalent to the FN SS109 round).
In a brief overview of the service life of the M16 series for American Rifleman in June, 2012, Martin K.A. Morgan encapsulated this history well:
In November 1983, the U.S. Marine Corps adopted a product-improved version of the M16A1 chambered for the 5.56×45 mm NATO round. The new rifle was called the M16A2 and it differed significantly from its predecessor: improved rear sights, a brass deflector, a heavier barrel and 1:7-inch rifling were among the changes. The M16A2 also replaced the M16A1’s “AUTO” selector setting with a “BURST” setting delivering three rounds with every trigger pull. The Army followed the Marine Corps’ adoption of the improved rifle in March 1986 when it ordered 100,176 M16A2 rifles from Colt. In September 1988, the U.S. government placed an initial order for 266,961 M16A2s with Fabrique Nationale’s North American subsidiary, FN Mfg., Inc. of Columbia, S.C. Late the following year, when 57,000 U.S. military personnel conducted the Operation Just Cause invasion of Panama, the M16A2 was used in combat for the first time.
For practical accuracy, the A2 had new sights, with a square front post; for range, a new round with a heavier bullet, and new rifling to match; and for durability, new stocks and handguards and significant metal reinforcement in the lower receiver’s weak areas, the pivot pin bosses and buffer tower.
The rifle was not without controversy in the Army. Indeed, contractors for the Army Research Institute for the Behavioral and Social Sciences examined the rifle and concluded that, as their paper’s abstract notes:
[U]se of the M16A2 rifle by the Army would be extremely problematic, a-fact due, in part, to the vast differences between the marksmanship training philosophies of the Army and the Marine Corps.
The Army had been researching improvements to the M16A1 for years, but hadn’t actually implemented any. In the foreword to the Army Research Institute paper, the word “problematic” crops up again and one gets the sense that the problem was this solution was Not Invented Here, and moreover, not developed the way the Army wanted to develop one.
Referring to earlier research, they wrote:
A detailed evaluation of M16Al performance was conducted to determine adequacy, peculiarities, etc. The findings clearly indicated that the M16Al was an adequate combat rifle; however, many shortcomings were identified that should be addressed in a new rifle or any rifle Product Improvement Program (PIP).
They considered that the improvements in the A2, listed below, were suitable only for the peculiar circumstances of Marine Corps service.
The Marine Corps test results stated the following advantages for the PIP [Product Improvement Program -Ed.] rifle:
- Ease of training (handling and ease of sight movement).
- Improved safety (no hazard when adjusting elevation on the rear sight even with loaded weapon).
- Increased effectiveness at long ranges (more hits, better accuracy, and greater penetration).
- Improved handling characteristics and durability in hand-to-hand close combat.
- Reduced barrel jump and muzzle climb during automatic and rapid fire.
- Increased contrast and less glare with square front sight post.
- Stronger, more durable and improved grasping characteristics of front handguard.
- Stronger barrel with quicker twist to take advantage of increased effectiveness provided by new ammunition.
- Improved sighting characteristics providing quick target acquisition for moving targets and better detection of targets in low level light conditions at close ranges, and more accurate long range fire by use of two modified rear sight apertures.
- Increased ammunition conservation and more effective use of ammunition with burst control device.
- Conformity to human factors standards by lengthening stock (alleviating bruised eyebrows, noses, and lips).
- Stronger, more durable stock.
- Stronger, more durable buttcap which also reduces slipping on the shoulder during firing.
- More controllable and comfortable pistol grip contoured to the shape of the hand.
- Improved brass deflector which protects left handed shooters from hot ejected brass casings.
- Can use NATO type improved ammunition (XM855) which provides improved performance and penetration at long ranges.
The Army evaluators were impressed by that list of solutions, but thought they all traced back to four specific USMC objectives or requirements:
The above list of advantages is very impressive. It appears that the rifle meets the primary requirements stated by the Marines:
- A sight adjustable to 800 meters.
- A bullet with better accuracy at 800 meters and the capability to penetrate all known helmets and body armor at ranges of 800 meters.
- A rifle with more durable plastic parts and barrel which will take a beating during bayonet training and extended field exercises.
- The replacement of the full automatic capability with a burst mode which fires a maximum of three rounds with each pull of the trigger.
…but they thought that the requirements were too Marine-centric.
The list, however, represents the objective and subjective evaluation of Marine Corps personnel who are emphasizing the most positive aspects of rifle characteristics as they pertain to envisioned Marine Corps requirements.
This is the first of a three part series. In the second part, tomorrow on WeaponsMan.com, the Army contractors damn the A2 with faint praise and list a litany of A1 shortcomings that they believed that the A2 did not resolve. In the third part, the modifications that they suggested in lieu of or in addition to the A2 mods are enumerated.
As it was, the contracting officer’s representative approved the paper in February, 1986. In March, and probably before any of the responsible officers read the paper, the Army went ahead and adopted the M16A2, just the way the Marines had shaken it out.
That makes this paper a time capsule.
Kevin was a former Special Forces weapons man (MOS 18B, before the 18 series, 11B with Skill Qualification Indicator of S). His focus was on weapons: their history, effects and employment. He started WeaponsMan.com in 2011 and operated it until he passed away in 2017. His work is being preserved here at the request of his family.