List of Colt AR-15 and M16 rifle variants

This article describes the many variations of the Colt AR-15 and M16 rifle family of weapons produced by Colt's Manufacturing Company. Weapons patterned on the original ArmaLite AR-15 design 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. 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.
Colt military models.
Colt has been the most visible producer of ArmaLite AR-15 pattern weapons, and the military designations M16 and M4 are 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 "R0". For the purposes of this table, the R0 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. 
Colt Armalite AR-15.
The original Armalite AR-15 models have the charging handle located on top of the upper receiver, protected within the carrying handle.
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 civilian models.
Colt's civilian line of semi-automatic Colt AR-15 rifles 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.
Glossary of terms.
Stock.
"Fixed Stocks"
"Retractable Stocks"
Barrel twist.
Note: Metric measurements are rounded upwards to the nearest digit.