AR-15 variants

This article is a review of many variations of the AR-15 family of weapons. Weapons patterned on the original ArmaLite AR-15 have been produced by numerous manufacturers and have been used by nations around the world, some of which created their own variations. The tables here are split in a variety of categories, and provide an overview of different subtypes of the platform. For purposes of these tables, bold model numbers are weapons used (or previously used) by the U.S. Military while italic model numbers are weapons for commercial or export sale. See Glossary of terms for an explanation of each column.

Numbered Colt military models
Colt has been the most visible producer of weapons of the AR-15 pattern, and the military designation M16 is heavily associated with the company. Colt has an intricate internal nomenclature system for its models, with a variety of suffixes and prefixes. Colt’s systems have generally followed the times and though its model numbers originally came without prefixes, with the need to separate weapons made for civilian consumption from those made for military and law enforcement use, military models became prefixed with the code “RO.” For the purposes of this table, the RO nomenclature is obviated as this terminology did not exist in all cases, but it can be understood to be present. Military/LE models are also easily identified by their three digit code in contrast to the four digit codes for civilian weapons.

Numbered Colt civilian models
Colt’s civilian line is identified by a four digit code following a specific prefix. Initially all Colt civilian weapons were listed with an “R” prefix, with this changing to “AR” following the passage of the Federal Assault Weapons Ban in 1994. Colt also produced a line of weapons aimed at target shooters under the “MT” prefix, which stood for Match Target, as well as, the Colt Accurized Rifle, which was the only model to feature the CR prefix. Most recently with the shift in marketing policy by Colt Defense, these weapons have been given the “LE” and "LT" prefix. The "LT" series is modified version of the Colt 6720 featuring a lightweight "pencil" barrel with a free floating rail system. Only 1500 of the "LT" series were produced. Currently, Colt Defense has no line targeted specifically at the private civilian market.

Colt military models without model numbers
In rare instances some Colt models have been produced without in house model numbers, or at least one which is readily apparent.

Diemaco/Colt Canada models
The Canadian company Colt Canada (formerly Diemaco) licensed production of a rifle (Colt Model 715) and carbine (Colt Model 725), but later went on to produce an entire line of AR-15/M16 pattern weapons developed independently. In May 2005, Colt's Manufacturing Company acquired Diemaco, and the name was changed to Colt Canada.

Colt Canada model changes and comments
When Diemaco became Colt Canada the marketing names for a number of products were changed, though some remained the same. Those that changed are listed below, with comments on what major changes Colt Canada made the models.

Stock
Fixed Stocks
 * A1: Fixed stock as used on M16 and M16A1. May or may not have a trapdoor to store a cleaning kit
 * A2: Improved stock used on M16A2. Longer by 5/8"
 * Tubular: Fixed tubular buttstock, similar to the 2nd Generation retractable unit, using a receiver extension and triangular rear with buttplate

Retractable Stocks
 * 1st Generation: 2-position sliding stock that resembled a shortened fixed buttstock
 * 2nd Generation: 2-position aluminum retractable stock
 * 3rd Generation: 2-position fiberlite retractable stock. Introduced 1985
 * Canadian 3rd Generation: 4-position fiberlite retractable stock fitted with rubber buttpad
 * 4th Generation: 4-position nylon retractable stock. Introduced 2002, designed by Picatinny Arsenal engineer Lily Ko with reinforced ribs, an angled buttplate, and a rear sling swivel
 * Retractable ACR: Similar in design to the so-called "Crane Stock" (initially fabricated by the Naval Surface Warfare Center Crane Division) essentially a 3rd generation unit with integrated cheek-rest
 * FPW Wire: Retractable wire stock similar in appearance to the stock used on the M3 submachine gun
 * Israeli: Rebuilt 3rd Generation stocks with 6 positions instead of 2

Fire control

 * S-1: The selector is Safe (S) – Semi-Automatic (1)
 * S-F: The selector is Safe (S) – Fully Automatic (F)
 * S-1-F: The selector is Safe (S) – Semi-Automatic (1) – Fully Automatic (F)
 * S-1–3: The selector is Safe (S) – Semi-Automatic (1) – 3-Round Limiter (3)
 * S-F-1–3: The selector is Safe (S) – Fully Automatic (F) – Semi-Automatic (1) – 3-Round Limiter (3). First Generation 4 position group
 * S-1–3-F: The selector is Safe (S) – Semi-Automatic (1) – 3-Round Limiter (3) – Fully Automatic (F). Second Generation 4 position group

Rear sight

 * A1: "Field sights" in which the rear sight is only adjustable for windage
 * A2: Rear sight adjustable for both windage and elevation
 * Flattop: Indicates carry handle and rear sight has been replaced with a MIL-STD-1913 rail. A detachable carry handle can be attached to the rail which features either A1 (Diemaco/Colt Canada) or A2 (Colt) sights
 * Weaver: Indicates carry handle and rear sight has been replaced with a Weaver-type rail. A detachable carry handle can be attached to the rail which features either A1 (Diemaco/Colt Canada) or A2 (Colt) sights

Barrel Profile

 * ArmaLite Early ArmaLite AR-15 ultra-lightweight 'Hollywood' turned-down profile barrel, 1:14 twist only
 * A1: Also referred to as the "lightweight" or "pencil" profile. Government-specified barrel profile increased to between 0.675 and 0.575 inches
 * A2: Also referred to as the "government" or "gov't" profile. Barrel profile for which the portion of the barrel in front of handguards is thickened to 0.715 inches
 * HBAR: A barrel that in some portion is thicker than government-profile, usually underneath the handguards
 * M4: Government barrel profile with small portion reduced to 0.575 inches to mount M203 grenade launcher
 * M4 HBAR: M4 barrel with portion under handguard thickened for sustained automatic fire
 * Super Heavy: Special Colt bull target/match barrel
 * SFW: Special Forces Weapon profile, A2 profile with "fat" portion forward of the sight triangle

Barrel twist
Note: Metric measurements are rounded upwards to the nearest digit.
 * 1:14: 1 right hand twist every 14 inches (356 mm)
 * 1:12: 1 right hand twist every 12 inches (305 mm) .223 Remington (US M193)
 * 1:10: 1 right hand twist every 10 inches (254 mm) 9 x 19 mm NATO
 * 1:9: 1 right hand twist every 9 inches (229 mm) .223 Remington & 5.56 x 45 mm NATO
 * 1:7: 1 right hand twist every 7 inches (178 mm) 5.56 x 45 mm NATO (NATO SS109)

Handguards

 * Triangular: Triangular rifle handguards
 * Short Triangular: Carbine length triangular handguards
 * Round: Smooth round rifle handguards
 * Short Round: Carbine length smooth round handguard
 * Ribbed: Ribbed round rifle handguards
 * Short Ribbed: Carbine length ribbed handguards
 * Square LMG: Special heavy handguards with integral vertical grip for use during sustained fire
 * FF Tube: Free-Float Tube
 * M4: Oval carbine handguards with double heatshields
 * Rail System: Handguards are replaced with a Rail Integration System

Muzzle device

 * Type 1 Duckbill: Original three-prong flash hider
 * Type 2 Duckbill: Also referred to as "three prong." A larger three-prong flash hider
 * A1: Also referred to as the "Birdcage" flash hider
 * A2: Birdcage flash hider with bottom slots closed off to act as muzzle compensator and to prevent dust from being blown into the shooters face while in the prone position
 * 3.5" Moderator or 4.5" Moderator: Either the 3.5-inch or 4.5-inch baffled moderators
 * Conical: A conical flash suppressor
 * ACR Compensator: Special anti-rise muzzle device developed specifically for the Colt ACR
 * Factory Compensator: Colt Factory muzzle brake compliant with the restrictions of the 1994 Federal Assault Weapons Ban