The M16A2 Rifle
There were twelve major changes from the M16A1 to the M16A2 and, although the rifles seem similar at first glance, they are two totally different weapons. Many improvements were necessary to accommodate the new M855 Ball and M856 tracer rounds. The twelve major variances between the Al and A2 are as follows:
1. The flash suppresser of the M16A1 is now a muzzle brake/ compensator on the M16A2. Instead of having vents all around the flash suppresser, the bottom has been left solid, which reduces muzzle climb and prevents dust from flying when firing from the prone position.
2. The barrel, from the front sight assembly to the flash suppressor/compensator, is heavier. The M16A1 rifles barrels were known to bend when paratroopers landed and the barrels hit the ground. When the Al barrels would heat up, sling tension could bend them. The new M16A2 barrels had a rifling twist of 1:7 inches to accommodate the SS109/M855 cartridge.
3.The front sight post on the M16A2 is square, contrasted to the round post of the M16A1.
4. The M16A2 handguard was redesigned to have an interchangeable, upper and lower, round ribbed handguard.
5. The slip-ring “delta ring” was redesigned and is now canted for easier removal of the hand-guards.
6. A spent shell deflector was added to the upper receiver behind the ejection port of the M16A2 to accommodate left-hand shooters and, as well, the pivot pin area of the upper receiver has been strengthened. The area around the buffer tube extension (takedown pin area) was strengthened to prevent cracking during hand-to-hand combat or from impact on the butt of the weapon while cushioning one’s fall.
7. The rear sight was redesigned. The 1.75mm and 5mm apertures made adjustable for windage as well as elevation. The maximum elevation setting is 800 meters. There is still an “L-shaped” sight aperture, and there is a 5mm aperture battle sight effective to 200 meters.
8. The forward assist assembly was changed from the “tear drop” style of the M16A1 to the new round “button” style forward assist assembly of the M16A2.
9. The pistol grip is now made of a stronger plastic (™Zytel), and incorporates a “swell” below the middle finger position.
10. The three-shot Burst selector lever setting of the M16A2 replaced the Auto setting of the M16A1.
11. The⅝-inch longer M16A2 stock is made from foam-filled nylon, said to be ten to twelve times stronger than the fibrite stocks of the M16 /M16A1.
12. The buttplate has been made stronger (™Zytel), and the entire buttplate is checkered. The trapdoor can be opened by hand rather requiring the tip of a cartridge.
Critics Attack the M16A2
There were critics who still found problems with the M16A2. One of the greatest criticisms was the substitution of the Burst mode for the Automatic mode selector option. The critics reasoned the M16 rifle was adopted because U.S. troops felt outgunned by the North Vietnamese Army/Viet Cong who were equipped with full-auto AK47s.
While, theoretically, the 3-round burst was more effective than full-auto fire, there was no substitute for a well-trained automatic rifleman. More recently, infantry units have noticed it takes more time to clear rooms and buildings in the MOUT (Military Operations in Urban Terrain) environment with the 3-round burst versus the full-auto mode and feel the full-auto option is desirable in those circumstances.
Not only was the conceptual validity of the three-round Burst under scrutiny, but the mechanical design as well. The burst mechanism does not recycle. If only two rounds were fired — because the trigger was not held long enough or the weapon ran out of ammunition — the next time the trigger was pulled only one round would fire.
Further, some critics found the sighting system too complex. The Canadian military addressed many of the issues brought up by American military critics. When Canada replaced their aging FN FAL 7.62mmNATO rifles, they modeled the new rifle after the M16A2. Their Diemaco-manufactured C7 was, virtually, an M16A2 that retained the rear sight and the full-auto setting of the M16A1.
Some critics did not like the fact that the new M855 cartridge could not be fired in the current issue M16 /M16A1 rifles without raising concerns that the fast l:7-inch rifling twist would more quickly burn out barrels during extended rapid fire.