Editing M16 rifle (section)

==Derivatives==
===Colt Commando (XM177 & GAU-5)===
{{Main|CAR-15}}
[[File:CCTwithGAU-5.jpg|thumb|upright|A USAF Combat Control Team member with a GAU-5 carbine and oversized flash suppressor]]

In Vietnam, some soldiers were issued a [[carbine]] version of the M16 named XM177. The XM177 had a shorter {{convert|10|in|mm|0|abbr=on}} barrel and a telescoping metal stock, which made it substantially lighter and more compact. It also possessed a combination flash hider/sound moderator to reduce the increased muzzle flash and loudened report. The Air Force's GAU-5/A (XM177) and the Army's XM177E1 variants differed over the latter's inclusion of a forward assist, although some GAU-5s do have the forward assist. The final Air Force GAU-5/A and Army XM177E2 had an {{convert|11.5|in|mm|0|abbr=on}} barrel with a longer flash/sound suppressor. The lengthening of the barrel was to support the attachment of Colt's own [[XM148 grenade launcher|XM148]] 40&nbsp;mm grenade launcher. These versions were also known as the Colt Commando model commonly referenced and marketed as the CAR-15. The variants were issued in limited numbers to special forces, helicopter crews, Air Force pilots, Air Force Security Police Military Working Dog (MWD) handlers, officers, radio operators, artillerymen, and troops other than front line riflemen. Some USAF GAU-5A/As were later equipped with even longer {{convert|14.5|in|mm|adj=on}} 1/12 rifled barrels as the two shorter versions were worn out. The {{convert|14.5|in|mm|adj=on}} barrel allowed the use of MILES gear and for bayonets to be used with the sub-machine guns (as the Air Force described them). By 1989, the Air Force started to replace the earlier barrels with 1/7 rifled models for use with the M855-round. The weapons were given the redesignation of GUU-5/P.

These were used by the British Special Air Service during the Falklands War.{{sfnp|Special Operations.Com ''SAS Weapons''|2000}}

===M4 carbine===
{{Main|M4 carbine}}
[[File:SCRange20034344940.jpg|thumb|right|An [[M4 carbine#M4A1|M4A1 carbine]] (foreground) and two M16A2s (background) being fired by U.S. Marines during a [[live fire exercise]]: though adopted in the 1990s and derived from the M16A2, the M4 carbine was part of a long line of short-barreled [[AR-15]] used in the U.S. military]]

The M4 carbine was developed from various outgrowths of these designs, including a number of {{convert|14.5|in|mm|0|adj=on}}-barreled A1 style carbines. The XM4 (Colt Model 720) started its trials in 1984, with a new {{convert|14.5|in|mm|abbr=in}} "stepped" barrel, case deflector, M16A2 rear sight, and a new elliptical handguard. The weapon became type classified as the "Carbine, 5.56mm, M4" in 1991. Officially adopted as a replacement for the M3 "Grease Gun" (and the [[M9 pistol|Beretta M9]] and M16A2 for select troops) in 1994, it was used with great success in the Balkans and in more recent conflicts, including the [[War in Afghanistan (2001–2021)|Afghanistan]] and [[2003 invasion of Iraq|Iraq]] theaters. The M4 carbine has a three-round [[Burst mode (firearm)|burst]] firing mode, while the M4A1 carbine has a [[automatic firearm|fully automatic]] firing mode. Both have a Picatinny rail on the upper receiver, allowing the carry handle/rear sight assembly to be replaced with other sighting devices.

====M4 Commando====
{{Main|CAR-15}}
Colt also returned to the original "Commando" idea, with its Model 733, essentially a simplified XM177E2 with the flash hider/sound moderator deleted and replaced with a normal birdcage-style flash hider. Over the different production runs Colt would assemble the guns with whatever parts were on hand, sometimes leading to the mixing of different M16, M16A1, M16A1E1, and M16A2 features on individual guns.

===M5 carbine===
[[File:Colt M5 at IDEX 2023.jpg|thumb|right|M5 carbine]]
The M5 carbine system was developed by Colt as an improvement on the M4 carbine. It incorporates a fully [[ambidextrous]] lower receiver, free-floating barrel and lengthened upper rail. The M5 carbine has four possible barrel lengths: 10.3, 11.5, 14.5 and 16.1 inches. Other M5 variants and calibers are the: M5 SCW (Sub-compact weapon) (5.56×45mm); M5 300 ([[.300 AAC Blackout]]); M5 SMG (9×19mm); CMK (7.62×39mm); M7 Battle Rifle (7.62×51mm) and Designated Marksman and Semi-Automatic Sniper System (both 5.56×45mm).

===Diemaco C7 and C8===
{{Main|Colt Canada C7 and C8}}
[[File:Canadian C7A2 Rifle.JPG|thumb|A Canadian soldier fires the current issue C7A2 rifle at the range with a [[C79 optical sight|C79]]A2 sight. This particular example is missing the standard TRIAD mount.]]

The [[Diemaco]] [[Colt Canada C7 and C8|C7 and C8]] are a family of rifles developed concurrently with the M16A2.{{sfnp|QORC, ''Colt Canada''|2012}} They are the standard issued rifle for the [[Canadian Armed Forces]], manufactured by Diemaco (currently [[Colt Canada]]). The C7 is a branch developed from the experimental M16A1E1. Like earlier M16s, it can be fired in either semi-automatic or automatic mode, instead of the burst function selected for the M16A2. The C7 also features the structural strengthening, improved handguards, and longer stock developed for the M16A2. Diemaco changed the trapdoor in the buttstock to make it easier to access and a spacer of {{convert|0.5|in|mm}} is available to adjust stock length to user preference, along with the addition of hammer-forged barrels. Unlike the American M16A2s, the Diemaco C7s utilize A1 style rear sights.  The Canadians originally desired to use a heavy barrel profile instead.

The C7 has been developed to the C7A1, with a [[Weaver rail]] on the upper receiver for a C79 3.4×28 optical sight, and to the C7A2, with different furniture and internal improvements. The Diemaco produced Weaver rail on the original C7A1 variants does not meet the M1913 "Picatinny" standard, leading to some problems with mounting commercial sights. This is easily remedied with minor modification to the upper receiver or the sight itself. Since Diemaco's acquisition by Colt to form Colt Canada, all Canadian produced flattop upper receivers are machined to the M1913 standard.

The C8 is the carbine version of the C7.{{sfnp|''Automatic Carbines''| 2008}} The C7 and C8 are also used by ''[[Hærens Jegerkommando]]'', ''[[Marinejegerkommandoen]]'' and [[Forsvarets Spesialkommando|FSK]] (Norway), [[Danish Defence|Denmark's Armed Forces]] (all branches), and the [[Netherlands Armed Forces]] as its main infantry weapon. Following trials, variants became the weapon of choice of the British SAS.

===Mk 4 Mod 0===
The Mk 4 Mod 0 was a variant of the M16A1 produced for the U.S. Navy SEALs during the Vietnam War and adopted in April 1970. It differed from the basic M16A1 primarily in being optimized for maritime operations and coming equipped with a sound suppressor. Most of the operating parts of the rifle were coated in Kal-Guard lubricant, a hole of {{convert|0.25|in|mm}} was drilled through the stock and buffer tube for drainage, and an O-ring was added to the end of the buffer assembly. The weapon could reportedly be carried to the depth of {{convert|200|ft|m}} in water without damage. The initial Mk 2 Mod 0 Blast Suppressor was based on the U.S. Army's Human Engineering Lab's (HEL) M4 noise suppressor. The HEL M4 vented gas directly from the action, requiring a modified bolt carrier. A gas deflector was added to the charging handle to prevent gas from contacting the user. Thus, the HEL M4 suppressor was permanently mounted though it allowed normal semi-automatic and automatic operation. If the HEL M4 suppressor were removed, the weapon would have to be manually cycled after each single shot. On the other hand, the Mk 2 Mod 0 blast suppressor was considered an integral part of the Mk 4 Mod 0 rifle, but it would function normally if the suppressor were removed. The Mk 2 Mod 0 blast suppressor also drained water much more quickly and did not require any modification to the bolt carrier or to the charging handle. In the late 1970s, the Mk 2 Mod 0 blast suppressor was replaced by the Mk 2 blast suppressor made by Knight's Armament Company (KAC). The KAC suppressor can be fully submerged and water will drain out in less than eight seconds. It will operate without degradation even if the rifle is fired at the maximum rate of fire. The U.S. Army replaced the HEL M4 with the much simpler Studies in Operational Negation of Insurgency and Counter-Subversion (SIONICS) MAW-A1 noise and flash suppressor.

===Mk 12 Special Purpose Rifle===
{{Main|Mk 12 Special Purpose Rifle}}
[[File:SPRCrane.jpg|thumb|US Navy Mk 12 Special Purpose Rifle]]

Developed to increase the effective range of soldiers in the designated marksman role, the U.S. Navy developed the Mk 12 Special Purpose Rifle (SPR). Configurations in service vary, but the core of the Mk 12 SPR is an 18" heavy barrel with muzzle brake and free float tube. This tube relieves pressure on the barrel caused by standard handguards and greatly increases the potential accuracy of the system. Also common are higher magnification optics ranging from the 6× power Trijicon ACOG to the Leupold Mark 4 Tactical rifle scopes. Firing Mk 262 Mod 0 ammunition with a 77gr Open tip Match bullet, the system has an official effective range of 600+ meters. However, published reports of confirmed kills beyond 800&nbsp;m from Iraq and Afghanistan were not uncommon.{{Citation needed|date=May 2010}}

===M231 Firing Port Weapon (FPW)===
[[File:M231 1.svg|thumb|right|M231 FPW]]

The [[M231 Firing Port Weapon]] (FPW) is an adapted version of the M16 assault rifle for firing from [[Firing port|ports]] on the [[M2 Bradley]]. The infantry's normal M16s are too long for use in a "buttoned up" fighting vehicle, so the FPW was developed to provide a suitable weapon for this role.

===Colt Model 655 and 656 "Sniper" variants===
With the expanding Vietnam War, Colt developed two rifles of the M16 pattern for evaluation as possible light sniper or designated marksman rifles. The Colt Model 655 M16A1 Special High Profile was essentially a standard A1 rifle with a heavier barrel and a scope bracket that attached to the rifle's carry handle. The Colt Model 656 M16A1 Special Low Profile had a special upper receiver with no carrying handle. Instead, it had a low-profile iron sight adjustable for windage and a Weaver base for mounting a scope, a precursor to the Colt and Picatinny rails. It also had a hooded front iron sight in addition to the heavy barrel. Both rifles came standard with either a Leatherwood/Realist scope 3–9× Adjustable Ranging Telescope. Some of them were fitted with a Sionics noise and flash suppressor. Neither of these rifles were ever standardized.

These weapons can be seen in many ways to be predecessors of the U.S. Army's [[Squad Designated Marksman Rifle|SDM-R]] and the USMC's [[Squad Advanced Marksman Rifle|SAM-R]] weapons.

===Mekut'zrar===
Israel was supplied with large numbers of M16A1 rifles by the US Government, many of which were shortened to make them more suitable for urban combat, storage in vehicles, and policing use by shortening them. The 20-inch M16A1 barrel was pruned back to just behind the gas port, while a new gas port was drilled to accommodate a carbine-length gas system as the front sight base was pinned in place. The barrel was also threaded for a standard M16A1 birdcage flash suppressor and the resulting barrel was just shy of 13-inch overall, and a CAR-15 type collapsible buttstock was fitted to replaced the fixed M16A1 fixed buttstock, thus they approximate the size of CAR-15 type carbines. The informal term "Mekut'zrar" translates to "sawed-off" or "shorty".<ref>{{cite web|url=https://gunsmagazine.com/guns/rifles/idf-colt-carbine/|author=Edward C. Ezell|title=IDF Colt Carbine|website=Guns Magazine|date=2021|access-date=August 25, 2024}}</ref>

===Others===
* The Chinese [[Norinco CQ]] is an unlicensed derivative of the M16A1 made specifically for export, with the most obvious external differences being in its handguard and [[revolver]]-style pistol grip.
** The '''ARMADA rifle''' (a copy of the Norinco CQ) and '''TRAILBLAZER carbine''' (a copy of the Norinco CQ Type A) are manufactured by S.A.M. – Shooter's Arms Manufacturing, a.k.a. Shooter's Arms Guns & Ammo Corporation, headquartered in [[Metro Cebu]], [[Republic of the Philippines]].
** The '''S-5.56 rifle''', a clone of the Type CQ, is manufactured by the [[Defense Industries Organization]] of [[Iran]]. The rifle itself is offered in two variants: the '''S-5.56 A1''' with a 19.9-inch barrel and 1:12 pitch rifling (1 turn in 305&nbsp;mm), optimized for the use of the M193 Ball cartridge; and the '''S-5.56 A3''' with a 20-inch barrel and a 1:7 pitch rifling (1 turn in 177, 8&nbsp;mm), optimized for the use of the SS109 cartridge.{{sfnp|''S-5.56 rifle''|2017}}
** The '''[[KH-2002]]''' is an Iranian [[bullpup]] conversion of the locally produced S-5.56 rifle. Iran intends to replace the standard-issue weapon of its armed forces with this rifle.
** The '''Terab rifle''' is a copy of the '''DIO S-5.56''' manufactured by the [[Military Industry Corporation]] of [[Sudan]].{{sfnp|''Terab''|2016}}
* The '''M16S1''' is the M16A1 rifle made under license by [[ST Kinetics]] in Singapore. It was the standard-issue weapon of the Singapore Armed Forces. It is being replaced by the newer SAR 21 in most branches. It is, in the meantime, the standard-issue weapon in the reserve forces.
* The [[MSSR rifle]] is a sniper rifle developed by the [[Philippine Marine Corps]] [[Philippine Marine Corps#Marine Scout Snipers|Scout Snipers]] that serves as their primary sniper weapon system.
* The [[Special Operations Assault Rifle (SOAR)]] assault carbine was developed by [[Ferfrans]] based on the M16 rifle. It is used by the [[Special Action Force]] of the [[Philippine National Police]].
* [[Republic of China Army|Taiwan]] uses piston-driven M16-based weapons as their standard rifle. These include the [[T65 assault rifle|T65]], [[T86 assault rifle|T86]] and [[T91 assault rifle]]s.
* Ukraine has announced plans in January 2017 for Ukroboronservis and [[Aeroscraft]] to produce the [[M4-WAC-47|M16 WAC47]], an accurized M4 variation that uses standard 7.62×39mm AK-47 magazines.{{sfnp|''M16 – WAC-47''|2017}}
* [[New Zealand Army#Equipment|New Zealand]] has adopted the [[Lewis Machine and Tool Company]]'s upgraded version of the M16 system to replace the [[Steyr AUG]]. This CQB16 rifle will be fielded in 2017 and is named [[Lewis Machine and Tool Company#MARS-L|MARS-L]] (Modular Ambidextrous Rifle System-Light).