m16 history

M16 and M4 rifles of the US Army (history timeline and Technical)

Last updated: November 18, 2022

The M16 has been used by the United States Army and various law enforcement agencies in the United States and allied countries for many years. For civilians, there is a gun like this that is semi-automatic only called an AR-15.

M16 rifles are produced both inside and outside the United States. There are many manufacturers, including Colt, FN, Hesse, Les Baer, Armalite, Bushmaster, Wilson Combat, and many others in the US. Outside the United States, including Canada and China, etc., there are also many manufacturers.

History of the M16

The development and service of the 5.56mm M16 rifle in the US military was a long story. Here’s a brief history, but only the ones that matter.

In the late 1940s, the United States Army’s Operations Research Office (ORO) investigated research on firearm effectiveness. The study concluded that an infantryman’s best option for a small arm is a .22-inch gun they can control easily, with high velocity and an effective firing range of 300 meters or beyond.


In 1953-1957, US Department of Defense. Further research was carried out in the “Project SALVO” project, which ultimately yielded the .22-inch ammunition that the infantry needed.

In 1957, the United States Army assigned Armalite to produce a small gun that was lightweight and controllable. Armalite gun designer Eugene Stoner began developing the rifle in .222 Remington and .22 Remington Magnum. It was chambered for .222 Remington Special, which was later renamed .223 Remington (5.56×45).

In 1958, Armalite Company delivers a new rifle, named the AR-15, to the US Army for testing. The rifle initially had problems with reliability and accuracy. Frustrated by the development of the AR-15, he sold the design to Colt.

ArmaLite AR-15 Prototype

In 1960, Eugene Stoner leaves Armalite to join Colt. In the same year, Colt demonstrates an AR-15 to the US Air Force Deputy Chief of Staff, who eventually purchases an AR rifle. 8,000 AR-15s are purchased by the US Air Force to use as a replacement for a small carbine.

In 1962, the United States Department of Defense Purchased 1,000 AR-15 rifles from Colt and sent them to South Vietnam for use in the field.

In 1963, Colt signed a contract to produce 85,000 rifles for the US Army as the XM16E1. The XM16E1 differs from an AR-15 or M16 in that it has an additional bolt carrier. This bolt carrier is necessary to use the hand to push the slide assembly into place to prevent the gun from jamming.


In 1964, the United States Air Force officially received the M16 rifle into service. This year, the U.S. Army received the XM16E1 rifle as a replacement for the 7.62mm M14 rifle.

M14 rifle
M14 rifle

In 1965, the M16 carbine was produced as the first model in the name of the CAR-15, intended for the United States Special Forces. Used in the Vietnam War This carbine has a barrel that is half the length of an M16, i.e. from 20 inches, reduced to 10 inches and shortening the stock by 3 inches. The stock is plastic. triangular barrel cover and light reduction sleeve 


In addition, the Colt company has developed a carbine from the CAR-15 model to the US Air Force’s survival gun. for the pilot whose plane crashed to use with a spherical barrel cover The buttstock is adjustable metal. and has a shortened pistol grip

In 1966, Colt signed a new contract to produce 840,000 guns for the US Army. 

In 1967, the US Army received the XM16E1 as the US Army’s standard gun. In the name of the 5.56 mm M16A1 rifle on February 28

In 1965-1967, the Report on the use of firearms in the field from Vietnam showed that the Stuttering M16 rifle distributed to the US military resulted in huge losses during the battle.

There are several reasons for this jamming. In the process of introducing new guns and bearings to be used in the military, the US Army changed the characteristics of the 7.62 mm cartridge from Dupont IMR to the standard 7.62 mm cartridge, m x 51 original NATO.

This caused the M16 bolt carrier to jam quickly if the gun was not cleaned well and often enough. The Colt Company had originally advertised that the M16 rifle required low maintenance, so in order to save money it was not necessary to supply equipment.

There are cleanings for this new M16 rifle, and soldiers who use them do not need to practice cleaning their guns.

Therefore, the soldiers did not have any prior experience in cleaning their guns. This lack of expertise led to many issues such as driving dirt into the gun which creates even more problems. When there is dirt build-up at the mouth of the gas pipe, it causes a higher pressure that leads to a high fire rate; however, this then reduces accuracy. Furthermore, more parts end up wearing out.

In 1967-1970, efforts were made to resolve this issue. The 5.56mm bearings were replaced with propellants so that less soot was deposited into the bearing housings. The barrel, chamber and bearings were chrome plated in order to prevent rust. 

Gun cleaning kits were provided to soldiers, and have been organized training in cleaning guns since then. At first, the soldiers had to carry a separate gun cleaning kit. But since the 1970s, all M16A1 rifles have been manufactured with a cleaning device compartment in the stock.

In 1970, a 30-round magazine was added to the original 20-round cartridge in order to match the cartridges of the Soviet and Chinese AK47 assault rifles.

In 1977-1979, NATO has accepted the 5.56 mm x 45 NATO cartridge as a new standard for military small arms instead of the old 7.62 mm x 51 NATO cartridge. This new cartridge was initially developed in conjunction with the FN Minimi machine gun.

The new cartridge is slightly heavier than the old one and has a slightly lower muzzle velocity than the old one. In order to have a longer effective range in relation to the ballistic coefficient of the new bullet, the SS109 (M855) bullet required a faster barrel twist rate than the 5.56mm x 45 M193 bullet. In order for the bullet to be stable, that is, the stability of the bullet has a fixed distance.

M193 bullets are suitable for use with guns with a barrel twist ratio of 1:12 (1 round in 12 inches) and SS109 bullets are suitable for use with With guns with a 1:7 barrel twist ratio (1 round in 7 inches). Some gun manufacturers have made their 5.56mm guns with a 1:9 barrel twist ratio, which has both advantages and disadvantages.

Inferior to old and new bearings, the Colt company developed a successor to the M16A1 gun suitable for use with 5.56 mm X 45 NATO SS109 ammunition and named the M16E1 gun according to the military order.

In 1982, the United States Department of Defense was renamed from M16A1 to M16A2.

Upgrade M16A1 to M16A2

  • The barrel is thicker and heavier than the M16A1’s caliber.
  • Round barrel cover instead of the original triangular barrel for better gun control interchange between upper and lower
  • The buttstock and pistol grip are made from a stronger plastic compound.
  • The center back has been redesigned and can now be adjusted to a variety of positions.
  • The upper frame has a recoil cartridge pad to prevent left-handed shooters from being hit.
  • For more accurate shots and to conserve ammunition, the firing stick has been changed from full automatic mode to 3-round bursts.
  • The newly designed dimming casing helps to better control muzzle deflection.
  • The firing sleeve is a pressure-deflecting device.
  • The barrel has a twist rate of 1 turn at a distance of 7 inches for firing 5.56mm x45 NATO or SS109 (M855) cartridges, which results in a higher effective firing range.
  • The M16A2 gun can fire the M193 cartridge using a barrel with 1 twist per 12 inches.
M16A1 and M16A2
Differences Between the M16A1 and M16A2

In 1983, the United States Marine Corps received a 5.56 mm M16A2 rifle for use in 1985. The United States Army officially received the 5.56mm M16A2 rifle and distributed it to the infantry.

In 1988, FN Company of Belgium U.S. sub-branch signed a contract with the US Department of Defense to produce the 5.56mm M16A2 rifle. Colt continues to develop and produce AR-15 rifles (M16 is a military designation), which are further to be sold in the civilian and law enforcement markets.

CharacteristicM16A1M16A2, M16A3, M16A4
Operation systemGas-OperatedGas-Operated
Blow-blackRecoil ActionRecoil Action
Ammunition5.56×45mm, M1935.56×45mm NATO/M855
Barrel20 inches20 inches
Caliber12 inches7 inches
Rate of fire650-750 RPM700-950 RPM
Automatic range150-200 RPM150-200 RPM (A3)
Burst mode range90 RPM (A2&A4)
Semi-auto range45-65 RPM45 RPM
Maximum range12-15 RPM12-15 RPM
Muzzle velocity990 MPS940 MPS
Weight without magazine2.89 KG3.4 KG
Weight with a loaded magazine20 , 30 round20 , 30 round
Overall length98.6 cm100.66 cm
Effective range503 yard656 yard
Maximum Effective Range2900 yard3937 yard
M16A1 vs M16A2, M16A3, M16A4

In 1994, the U.S. Army received the new M16 rifle into service. It includes the M16A3 rifle, the M16A4 rifle, the M4 carbine, and the M4A1 carbine.

M4A1 carbine

The M16A4 has the same firing system as the M16A2, while the M16A3 has changed from 3-shot burst to fully automatic firing. The M4 and M4A1 carbine are upgraded after the CAR-15 carbine.

Technical Of M16 

All M16 style guns are pretty much the same. They work with gas, which you can control your shots with as you wish. They are fed with magazines, but civilian AR-15s are semi-automatic only.

Gas powered System

The heart of the M16 is a direct gas-powered system developed by Eugene Stoner in the early 1950s. The hot gases from the combustion of the driving powder will exit the gas holes. Before reaching the mouth of the barrel and entering the stainless gas tube, the end of the gas tube will end at the gas receiver tube located at the top of the slide frame.

The hot gas expands the gas chamber, causing the ball assembly to move backwards. The ball bearing bolt is forced to rotate along the notch on the ball frame, and the head of the slider will rotate accordingly, releasing itself from interrupting the bolt. The slewing frame will continue to move towards the rear according to inertia and residual thrust in the barrel. The casing is then retracted and the slide guide assembly is compressed into the axis.

When the slider frame moves back into place by the power of the damping leaf springs, it will bring the top bullet in the magazine into the chamber in the final stages of forward movement. The slide guide pin forces the slide head along a notch on the slide guide frame, which causes the head of the sled to rotate and interrupt the bolt with the end of the barrel. The sledge head has a 7-teeth locking gear; the 8th tooth is on the cartridge holder.

The M16A1 in military use and the AR-15 in civilian use have a bolt carrier. The ball drop lever consists of a button, which is compressed with the spring. The inner end, when pressed, collides with the notch on the right side of the ball guide.

To push the spool guide frame forward in the event that the shock absorber springs are unable to push the spool head back to the front as far as possible (such as if there is dirt on the frame or in the chamber) The gun will not be able to fire if the bolt head and bolt guide are not fully forward in the bolted position. The slider head and slider guide frame are both chrome plated to prevent rust.

The M16 type gun will have a steel slide stop. This will stop the slide guide frame in the open position when the last shot is fired. To release, press the slide guide release button located on the left side of the trigger housing, above the magazine. The “T” shaped slide retainer is located at the rear of the slide frame, above the buttstock, and will not move while firing a gun.

Trigger Kit

Trigger kit: It consists of a Trigger, Guard Roll, Pin Trigger, Spring Trigger, Pin Hammer, Pin Disconnector, a firing lever, and an automatic firing mode. The firing lever is located on the left side of the frame and is conveniently operated by the thumb of the right hand. It has three positions: untriggered (safe), single fire (semi), and automatic fire (auto) (M16A1 and A3) or series three shots (burst)

Shell Ejector 

Shell ejector hole It’s on the right side of the gun frame. A spring-loaded dust cover is closed. It opens automatically when the bolt carrier moves rearward. The M16A2 has a triangular casing reflector mounted on the carriage just behind the cartridge extractor. Helps to keep safety when shooting left-handed.

M16 style guns are fed with aluminum 20 rounds and 30 rounds are now being replaced with steel ones to increase the efficiency of loading ammunition. In the civilian market there is a wide variety of magazines and sizes, ranging from 5 rounds to 100 and 120 “C” (c-Mag) style magazines.


The gun frame is made of aluminum alloy. It is divided into two parts: the upper frame and the lower frame. The upper frame is the slide frame, and the lower frame is the trigger frame. Two bolts hold the two frames together.

To remove the gun, push the rear bolt on the pistol grip to the right. Lift up the upper spool frame and remove the spool guide and spool holder from the upper frame. Remove the front fuselage bolt and separate the two halves of the gun body.

The advantage of this type of gun is that the upper and lower assemblies can be combined. Because the upper frame is part of the slider frame, there are barrels from 7 inches to 24 inches in length, both normal and heavy, in muzzle widths ranging from .17 Remington to .50 BMG (12.7 mmx99).

A variety of triggers, dampers, pistol grips, stocks and other accessories are all advantageous and suitable for use. from special forces to law enforcement

Cover and Handle

The barrel cover and the gun handle are both made of black plastic, originally used in AR-15 and M16A1 guns, and later guns have changed the barrel cover to a round shape. The top and bottom can be assembled interchangeably. M16A1, but it is slightly longer.

The drawback of the stoner system gun is that it cannot be converted to a folding stock. Must use a sliding type only This reduces the length of the gun by about half of the standard stock.

bayonet mount

M16 rifles can generally be equipped with a gun sling and bayonet. The original M16 suppressor was a triangular type with three openings, but the new one was changed to a birdcage type. There are 4 or 5 openings on the M16A1 and M16A2, reducing muzzle rise during firing.

Install a grenade launcher

All M16A1, M16A2, M16A3, and M16A4 guns can be mounted under the barrel of a 40 mm M203 grenade launcher by removing the barrel cover and installing a grenade launcher instead. The center of the grenade launcher must be brought to be installed on the handle of the gun.


The standard sight for the M16 gun consists of a front sight and a rear sight. The front center is the same for all models. It has a bumper frame mounted on the front center platform. The M16A1 rear sight is collapsible, mounted in the pistol grip. It has a lateral correction and two firing range settings.

The rear sight of the M16A2 can be folded, but has a different use in that the smaller sight is used in daylight and large holes are used in low light. Range adjustment is done by turning the revolver at the bottom of the rear sight. The M16A3 and M16A4 have the same rear sight as the M16A2, but the handle is removable and a special mounting rail is attached to the top of the gun frame. Three vehicles can be equipped with various types of aiming aids.


In 1994, the original idea of switching from a handgun to a more effective shoulder pistol resurfaced in the US Army. The year 1941, which at that time was using the M1 carbine, was a good idea that would not be lost and died, so the United States Army therefore received a Colt Model 720 for use in service (The short-barreled version of the M16A2 rifle, about 80% of the spare parts are interchangeable.) and officially changed its name to the 5.56mm M4 carbine.


The M4 is intended to replace the M9 pistol (Beretta 92FS), the old M3A1 submachine gun and some M16A2 rifles (this plan may change in the US Army. Due to the development of the XM-29 OICW and XM8 carbine), the 5.56mm M4 carbine is small, compact, lightweight, easy to use and carry.

The United States Special Operations Command (US Special Operations Command, USSOCOM) has therefore aimed this M 4 gun as a multipurpose tool. For those special warriors who want to use a small, compact gun for close quarters combat (CQB) combat.

Colt, which has signed a contract to produce a new M4 rifle based on the M16A3, features a flat top barrel and a special Picatinny rail mount, replacing the handle on the original M16A2/M4. This allows for the attachment of various optics and other accessories.

Another change from the M4A1 to the M4 is that the trigger unit has been changed to automatic fire instead of a 3-round burst. It is also suitable for confined space combat (CQB) and urban combat because of its small size, compactness, accuracy and powerful firepower.

Although the M4A1 carbine does not have the same effective range as the M16, the military has determined that engagement with a rifle at distances beyond 300 meters is unnecessary.

Colt M4 Commando Full-Auto

Colt has produced Machine gun or submachine gun model M4 Commando which comes out to be used as well, with the same characteristics as the M4A1 gun, but the barrel has been shortened to 29 cm, making the gun longer.

When the buttstock is moved out 76 cm and 68 cm when in Weight when loaded down to 2.44 kg and 2.89 kg when loaded with a magazine with 30 rounds.

Summary of M16 and M4

Colt has had great success in purchasing the AR-15 designed by Eugene Stoner since 1958 and developing it into a top-of-the-line weapon that has been adopted by the U.S. Army. And friendly countries around the world, which are estimated to have a total of about 15 million rifles

The latest guns are the M16A3, M16A4, M4, and M4A1 that entered service in the United States Army in 1994. They still have a bright future. Although there are competitors attacking the unreliable gun operation system, and the number of shots from the start of the fire to the gun jam is so low that the gun needs to be cleaned often, these guns are still popular choices for many.

However, Colt’s contract with the US government will end in 2009, with HK getting a new contract to use instead.

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