SOG's favourite weapon...

The CAR-15 Commando was not initially part of the CAR-15 Military Weapons System, but was added in 1966 in response to the US military's desire for a shorter M16 and the Model 607 SMG's inadequacies. Colt engineer Rob Roy designed a simpler two-position telescoping tubular aluminum buttstock to replace the complicated extending triangular version. The fragile and ad hoc triangular handguards were replaced by reinforced round handguards. Each half of the round handguard was identical, simplifying logistics by not requiring a top/bottom or left/right pair. The Model 609 Commando had a forward assist, while the Model 610 Commando did not. A Model 610B with a four-position selector was available, but not used by the U.S. military. All versions were equipped with the 4.25-inch long moderator.

The Model 610 was classified as the XM177 but adopted by the Air Force as the GAU-5/A Submachine Gun (GAU = Gun, Aircraft, Unit.) The Army purchased 2,815 Model 609 CAR-15 Commandos on June 28, 1966, which were officially designated Submachine Gun, 5.56 mm, XM177E1. As part of the contract, Colt was supposed to supply each XM177E1s with seven 30-round magazines, but Colt was unable to build a reliable 30-round curved magazine that would fit in the M16 magwell, so most XM177E1s were shipped with 20-round magazines. The exception was 5th Special Forces Group, who received a total of four early 30-round magazines. Colt completed delivery of the purchased XM177E1s in March 1967.

SOG Recon Team members would sometimes use a standard Colt hand grip as a field expedient foreward grip. (not to be confused with the issue Colt fore-grip that fixes to the bayonet lug

In 1967, in response to field testing, Colt lengthened the Commando's barrel from 10 inches to 11.5 inches. The increased length reduced noise and muzzle flash, and allowed fitting of the Colt XM148 grenade launcher. A metal boss was added to the moderator for mounting of the XM148 and rifle grenades. The chambers were chrome-plated. The Commandos with the longer barrels were called the Model 629 and Model 649. The Model 629 Commando had a forward assist; the Model 649 Commando did not.

In April 1967, the Army purchased 510 Colt 629 Commandos for use with by troops assigned to the Military Assistance Command, Vietnam Studies and Observations Group (MACV-SOG), and designated them XM177E2. Delivery was completed by the end of September 1967. The Air Force adopted a similar model without the forward assist feature as the GAU-5A/A. Sources debate whether or not this was a Colt Model 630 or 649. According to John Plaster and other sources, the lack of 30 round magazines continued to be problematic and SOG Special Forces operators resorted to pooling their personal resources and purchasing the larger capacity magazines on the civilian U.S. market. Problems with range, accuracy, barrel fouling, and usage of tracer bullets continued to plague the XM177 series, but Colt estimated that it would take a six-month $400,000 program to do a complete ballistic and kinematic study. There were also recommendations for a 29-month $635,000 research and development program. Both recommendations were declined by the U.S. military as American ground force involvement in the Vietnam War was gradually winding down. Production of the CAR-15 Commando ended in 1970.

A 40 round M16 magazine that can be seen in use in a few photos of SOG teams.

M203 Grenade Launcher: SOG teams were some of the first to use the XM203 Under-slung grenade launcher. The M203 grenade launcher has been developed between 1967 and 1968 by the AAI Corporation of USA on the contract from US Army. this contract has been issued on the basis of the experience, gained by the US armed forces in Vietnam with the M79 40mm grenade launcher (which was successful design but required an additional personal defense weapon to be carried by grenadier) and unsuccessful XM-148/CG-4 40mm underbarrel grenade launcher, developed in mid-sixties by Colt in attempt to cure deficiencies of the M79. The new underbarrel grenade launcher was intended to be used with all available 40mm ammunition, and to be attached to the existing infantry rifle then in service, the M16A1.In the late 1968 the AAI design has been type classified as XM203, and in early 1970 first M203 units went to Vietnam for field evaluation. After successful tests US Army ordered large quantities of M203, and since AAI had no resources fore mass production, the manufacturing contract has been issued to Colt. latter on, more or less exact copies of M203 were produced in Egypt, South Korea and Bulgaria (as UBGL-M1, with mount suitable for Kalashnikov AKM and AK-74 type rifles). During the 1990s, M203 went into several modifications, such as shorter-barreled M203A2 (with 9 inch barrel, as opposed to standard 12 inch barrel), intended for shorter M4 carbines used by US SOCOM, as well as versions with MIL-STD 1913 (Picatinny rail) compatible mounts. M203 launchers are still being used by US armed forces, and by many other armies, including those of Australia, Israel, South Korea, Philippines, Turkey and some others.

The M203 is a single-shot, breech-loading weapon with rifled barrel. The loading is achieved by sliding the aluminum barrel forward, then inserting the round of ammunition into the breech and sliding the loaded barrel back into the battery. The barrel is held in-battery by the manually controlled lock, which is disengaged by depressing the barrel catch lever at the left side of the launcher, above the middle of the barrel. The loaded cartridge is held at the breech face by the extractor claws, and remains stationary when barrel is opened forward. Once the barrel clears the fired case or unfired round, it is free to fall down from the breech face, so the next round can me loaded if necessary. The self-cocking firing unit with its own trigger is located at the rear of the M203 receiver, also made from aluminum alloy. The manual safety in the form of the swinging flap is located inside the trigger guard, just ahead of the trigger. The rear part of the barrel is covered with polymer handgrip. The standard M203 easily installs on the M16A1 or M16A2 type rifle, and installation requires about 5 minutes of work and a standard screwdriver for clamping screws. If necessary, M203 can be mounted on a separate shoulder-stock / pistol grip assemblies (available from several companies, such as Colt or Knight's Armament) to be used as a stand-alone weapon. Standard sights for M203 are of ladder type, and graduated from 50 to 250 meters in 50m increments. The optional quadrant sight can be installed on the left side of the M16A1/A2 carrying handle, and it allows aiming at the ranges of up to 400 meters.