Model 639 (Commercial/Export variant of the XM177E2). In the 1970's the ATF classified the XM177E2 style 4.5" moderator as a suppressor, hence carbines manufactured after this point are fitted with a standard flash hider.

After 1973, Colt made several lightweight versions of the M16 and Commando rifles, Model 653 for use with police and security forces, as well as civilian sales worldwide. These had the features of the XM177 carbine series, including the telescoping stock, but have either a 14.5" or a 16" lightweight barrel, depending on the demands of the customer, whether domestic or foreign.

In 1985, Colt also made the Model 733, which is an 11.5" barreled version of the Model 653, intended for tactical police and security work. Later manufactured versions of both guns have A2 style heavy barrels. The Model 723 is a 733 designed for export for the UAE and used by US Delta Force.

The Model 727 is a variant is nearly identical to the late-model Colt 723 except that it has an M16A2-style upper receiver (with A2 rear sight) rather than the "A1E1"-style receiver of the 723. This carbine was used by U.S. Navy SEAL platoons and some other U.S. SOCOM elements (including the U.S. Army 75th Ranger Regiment) from the late-1980s until the mid-1990s, when the M4A1 entered service.

M16's Carbine/Commando
Model 639 (Late CAR-15 with Birdcage Flash Hider)
Model 733 (Early Model With A1 Receiver)
Model 733 (Late Model With A2 Receiver)
Model 653 (M16A1 Carbine)
Model 723 (Early M16A2 Carbine)
Model 727 (Late M16A2 Carbine)