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Colt M16A1



Right side view of M16A1 (model R613) full size assault rifle.

Source: Dragunova - © GNU Attribution Share Alike license

United States
Assault rifle
Entered service
1964 for M16
1969 for M16A1
In service
Eugene Stoner
1967 - 1982 for M16A1
United States - Colt
Philippines - Elisco Tool and Manufacturing
South Korea - Daewoo
ArmaLite model index
Rifle, Caliber 5.56 mm, M16
Official designation



The M16A1 is an early Cold War assault rifle of US origin. The M16 was a giant leap forward in firearms design and the first standard issue assault rifle adopted by US forces. the M16's design stems from the ArmaLite AR-15, but the name Colt is best known for producing the first generation of the M16 family. The M16 and M16A1 were used by US forces throughout the Vietnam War. It proved to be a promising weapon, but suffered from a number of flaws, which were remedied during the Vietnam war and in the later M16A2 series of rifles.


The M16 has a conventional layout while the M16 seet the standard on what is nowadays called a conventional layout. The M16 is based on the straight line principle. The shoulder stock, action and barrel are all in one line resulting in reduced recoil. In order to aim properly the sights have been raised. The rear sight base also functions as a carry handle for the weapon. The receiver is made of aluminum with the barrel, bolt and other parts in the mechanism made of steel. The forearms, pistol grip and stock are made of plastics. The M16 uses direct impingement gas operation. When a shot is fired high pressure gasses build up in the barrel. In the M16 these gasses are tapped via a port in the front sigh base and through a gas tube above the barrel they cycle the system. This design reduces the amount of moving parts significantly, but the gasses foul the moving parts easily. The M16 forms the basis for many variants that range from very compact weapons to light machine guns.


The M16A1 fires the 5.56x45mm M193 round which was specifically designed for this weapon. For a long time the M16 was issued with 20 round magazines as the development of a 30 round magazine proved difficult. A slightly curved 30 round magazine proved to be the solution. The M16A1 is a select-fire weapon with a cyclic rate of fire of 700 to 900 rounds per minute. The maximum effective range is 400 m for the M16A1 and somewhat less for variants with shorter barrels. Overall the M16A1 is a good rifle. It is very light, accurate, ergonomic and has a very low recoil. The main drawback is its lack of reliability in certain conditions.


The US Air Force was the first to adopt the M16. The US Army adopted an improved model with forward assists as the M16A1, followed by the US Marine Corps. The introduction of the M16A2 in the mid 1980's resulted in the graduel withdrawal of most first generation models from US service. The M16A1 remains in service with various nations around the world, but is more and more relegated to a reserve role.



M16A1 with the recognizable triangular handguard (top) and M16A1 with M203 grenade launcher (bottom).
Source: Unknown author - © Copyright lies with original owner

Variants of the M16 rifle

M16: The Colt R604 was adopted by the US Air Force as the M16. The M16 has no forward assist. Early variants had a three prong flash hider. This was later replaced by a birdcage flash hider as on the M16A1. For export sales the R604 was designated R614.

M16A1: The M16A1 is the US army version of the M16. It is similar to the M16, but is fitted with a forward assist to manually push the bolt forward in case the bullet fails to seat in the chamber. The forward assist is fitted on the right side of the receiver near the stock. For export sales the R603 was designated R613.

The M16A1 is also often fitted with the M203 grenade launcher. The launcher comes with a proprietary forearm with ladder sight for the launcher on top.


Facts M16 M16A1
United States
Assault rifle
5.56x45mm M193
20, 30 round detachable box
Barrel length
508 mm
6 grooves, right hand 305mm twist
Muzzle velocity
975 m/s
Gas operated, direct impingement, rotating bolt
Fire selector
0 - 1 - F
Rate of fire
650 - 750 rpm
Stock type
986 mm
3.1 kg empty
Iron sights, post front and flip aperture rear

Related articles

Colt M16A2

The M16A2 is a further developed rifle based on the M16A1. One of the major differences is that the M16A2 is chambered for the NATO variant of the 5.56x45mm cartridge.

Colt Commando

The Colt Commando series was developed as a very compact version of the full size rifle for special operations use.

Colt CAR-15

The CAR-15 is the carbine variant of the M16A1. It has a shorter barrel and retractable stock.

Colt M16A1 HBAR

The M16A1 HB is a light support weapon variant of the M16A1. It has a heavier barrel, bipod and some variants fire from the open bolt position.


The M203 under barrel grenade launcher was developed specifically for use on the M16 and M16A1 assault rifle.