Staff Writer (Updated: 6/14/2016):
The Commando retained much of the form and function of the AR-15/M16 lines though the shorter barrel assembly and telescoping shoulder stock effected accuracy somewhat. A special muzzle component was designed to retard muzzle flash as well as suppress the exiting action though the Commando was far from a "silenced" weapon. Nevertheless, its handy proportions made for a compact weapon where and when it was needed.
The United States Army contracted for over 2,800 of this special weapons system from 1966 onwards. After some time in-the-field, lessons with the new weapon were learned and Colt responded to reports with a longer barrel of 11.5 inches which aided accuracy and noise reduction some. The longer barrel also added support for the XM148 Under Barrel Grenade Launcher (UBGL) unit to broaden the warfighter's tactical value. The revised Commando was Colt's Model 629 and Model 649, these differentiated by the 649's lack of a forward-assist feature. Over 500 of the new weapons were then acquired by the Army (as XM177E2) from 1967 onwards.
The Commando was in production until 1970 and the U.S. involvement in Vietnam ended in 1975. However, the Commando soldiered on in the post-war world with some units still in use across South America in the various regional conflicts and civil wars there. Additional service saw them fielded with Israel during the Yom Kipper War.
The modern M4 Carbine went on to replace the Commando in the same assault carbine role during the 1980s and has gone on to see much more widespread service since.