Posted by on 1/5/2022 to
The AR-15 was invented in the late ’50s by Eugene Stoner. He successfully combined cutting-edge materials, superior science, and intelligent engineering techniques to create a rifle that would revolutionize firearms. It was available for purchase in the civilian market even before the military made their changes and made it the official service rifle. The military version has some differences and AR-15 products that comply with these standards often label themselves ‘Mil- Spec’ meaning ‘made to military specifications.
The military version of the AR-15, the M16, has seen some changes over the years. There is the first version: M16A1 and the most recent version the M16A4, and iterations in between. It can be confusing which one is which, especially since changes can be easily made to the point where you may have a hybrid with components of different versions. The original AR-15 and the M16 had a direct gas impingement system and a buffer system. The AR-15 and the M16 originally used the 223 Remington caliber, however. now the M16 uses the 5.56 NATO caliber. There were many other changes made to the M16, though many of them are so minor, that pretty much no one noticed. The list below details the different versions, their names, and the bigger, more general changes:
M16A1:
With the addition of the forward assist, the first change was made and the rifle was renamed the XM16E1. It was soon renamed again as the M16A1, which differed from the original AR-15 with its forward assist, chrome-plated bore, and a 30 round magazine. The barrel has a 1:12 twist rate. It also has a triangular handguard and a four-slot “Birdcage” muzzle device.
M16A2:
In 1982 some changes were made and the A2 became the official primary infantry rifle. It has a heavier barrel with a 1:7 twist rate. The rear sights were made adjustable for both range and windage. The buttstock saw a lot of attention as it was made stronger and increased in size. The handguard is made of two identical halves and was round instead of triangular which is stronger and allows for a better grip. To save on ammunition and promote accuracy, the full-automatic fire setting was changed to a 3 round burst. It also made a distinction between the upper receiver and the lower receiver. It has a 5 slot “Birdcage” muzzle device.
M16A3:
The A3 changes the 3 burst fire option back to the original full-automatic, and that’s about it.
M16A4:
Has a removable carry handle and a handguard with a picattiny rail. Along with the M4 it is ready for an optic. A4 has the 3 burst fire mode instead of full-automatic.
M4:
The M4 carbine was initially created for the special forces. With a telescoping stock and a shorter barrel(14.5” as opposed to 20”), it can be made smaller, which makes it easier to transport and carry. Since the soldiers who carry this often use it indoors and at close range in smaller, more confined spaces, it makes sense to have a shorter weapon for them. This can have either standard sights or attached optics.