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The M16 Rifle: A Brief History and Overview

The M16 Rifle

The M16 rifle was first developed in the early 1960s as a replacement for the M14 rifle. It was designed to be lighter and more accurate than the M14, which is a battle rifle, and it featured a new high-velocity cartridge – 5.56X45mm NATO. The M16 quickly became the standard-issue rifle for the US military, and it has been used in conflicts all over the world. Over the years, the M16 has undergone several modifications, but it remains one of the most popular rifles in use today. Thanks to its lightweight design and accuracy, the M16 is ideal for a wide range of situations, making it a versatile and reliable weapon for soldiers.

The M16 Rifle in Vietnam

The original M16 had a 20″ barrel and a 1/12 or 1/14 twist, which made it ideal for shooting 55gr M193 ammo. It also had a three-pronged flash suppressor, triangle handguards, and a fixed stock.

The M16 was originally designed without a forward assist, but this was later added to the design. The selector switch on the M16 had three positions: safe, semi-automatic, and fully automatic.

Problems with the M16 rifle in Vietnam

The sudden adoption, along with it’s revolutionary design led to a variety of issues. They would unfortunately need to be worked out in the middle of a bloody conflict.

  • The M16 was incorrectly labeled by the military as being “self cleaning”, so no cleaning kits were issued.
  • The original M16 lacked a chrome lined chamber and bore to protect against corrosion and pitting.
  • The US military went against recommendations and used a stick powder instead of a ball powder which led to more fouling.

These problems, combined with the harsh jungle environment was a terrible combination for the M16 and its reputation quickly became tarnished. Especially compared to the AK-47, which Vietnamese troops were using.

The lasting effects of this conflict would create a stigma around the M16 and AR-15 platform that would be difficult for them to shake.


The US military would eventually figure out the problems with the M16 and a made an updated version which would address many of the concerns in the original model.

The M16A1 featured the following additions:

  • Forward assist
  • Raised fence around the magazine release
  • Chrome lined barrel (bore and chamber)
  • A1 birdcage flash hider
  • Parkerized and notched (to work with the forward assist) bolt carrier group

Additionally, cleaning kits were issued and the powder in the ammo was changed. These series of changes vastly improved the reliability of the M16 rifle in Vietnam from that time forward.

The M16A1 would be standard issue from 1967 to 1985.


In 1983, the M16 rifle would go through another makeover, many of which were prompted by the USMC. This time the changes included the following:

  • Longer, stronger buttstock
  • Slightly different pistol grip
  • Round handguards
  • Brass deflector
  • Closed bottom flash hider (to keep from kicking up dust when shooting prone)
  • Heavier “government profile” barrel (light under the handguards)
  • 1/7 twist barrel
  • Sights were changed so they could account for windage and elevation
  • Instead of “auto”, the M16A2 would be capable of semi or 3-round burst

The purpose of the change in barrel twist was to accommodate the new “green tip” 62gr M855 (steel penetrator) and M856 (tracer) rounds. A faster twist is required to properly stabilize these longer bullets.


Only one change was made to the A3, and it was only in limited used, mostly by the US Navy. Instead of being 3-round burst like the M16A2, it was capable of full auto.


The M16A4 was adopted in 1997. The changes that were made included:

  • Flat top upper for ease in mounting optics
  • KAC M5 RAS rail system

Originally produced by Colt, FN would eventually take over the contract for the military.

While the M16 rifle is still in limited use today, most of the military is using the M4 these days, which is just a shortened variant of the M16A4, with a collapsible buttstock.

The M16 rifle has been through a lot of changes since it was first introduced in the 1960s. It has proven itself in several wars since then, and it is more versatile and more reliable than ever.

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