The Colt CGL-4 (Colt Grenade Launcher, officially designated Launcher, Grenade, 40mm, XM148)[1] was a prototype American underbarrel grenade launcher designed by Karl R. Lewis and Robert E. Roy in 1964[2] and produced from 1964 to 1970 by Colt Industries Inc. Colt's entrant into a competition set up by the United Stated Army, the CGL-4 was the first underbarrel grenade launcher to enter service in the United States Army.

History[edit | edit source]

In 1963, the United States Army organized a competition of sorts to design a new underslung grenade launcher which could be mounted on the then-nascent AR-15 platform, which was undergoing early testing around that time.[3] Colt tasked design engineer Karl Lewis to design the weapon; Lewis, with the assistance of Robert E. Roy, "wrote the specifications, designed the launcher, drew all the original prints, and had a working model built", allegedly in just 47 days.[4]

The weapon was then tested at Ford Benning agaisnst designs by Springfield Armory, Philco-Ford, AAI[3] and a U.S. Government think tank;[4] the CGL-4 was selected in March 1965 against the other designs, with a contract signed for 30 production models. The weapon was then officially designated the Launcher, Grenade, 40mm, XM148. A further order for 10,500 launchers was issued in January 1966; however, production issues and various other problems meant that the first batch of 1,764 launchers did not arrive for combat testing in Vietnam until December that year.[3]

Field testing of the weapon was carried out by some twelve units from 6 divisions, all of whom were stationed in different areas of Vietnam.[5] At first, the weapon seemed promising, as troops praised the "tactical advantage of both the point fire and area fire systems", and was also well-received by both the Navy SEALs and the Australian SAS, the latter of whom mounted the XM148 on their L1A1 SLRs with some modifications.[3]

Further testing however revealed a whole host of other problems. Testing revealed that when the XM148 was used, the grenadier had slower reaction time, decreased their rate of fire, hampered their movement in dense vegetation and they had to spend longer caring for their weapon. Worryingly, the XM148 itself had even more issues, particularly a complex sighting system that was prone to snagging on brush and other gunk, the complex trigger mechanism which proved to be able to also snag on brush, the amount of force required to cock the weapon and the weapon itself also being difficult to repair. Using a bayonet was also impossible; firing the XM148 with a bayonet on blew the bayonet off the barrel. Troops as a whole found that the CGL-4 was too fragile for field use.[3]

Despite these issues, at least one unit, the 1st Air Cavalry Division, is known to have made use of the XM148, but noted that the weapon "proved unsatisfactory in infantry units due to its lack of durability", with the USARV requesting that the weapons be instead turned in; however, said unit continued using the XM148, albeit coaxially mounted on M60 machine guns mounted on OH-13 helicopters, claiming that firepower on said helicopters was "significantly increased".[3]

Despite all efforts from Colt to rectify the design's ever increasing list of problems, the Army Concept Team stationed in Vietnam ultimately deemed the CGL-4 unfit for service, recommending that they be withdrawn from service and replaced by a newer, more-reliable launcher. This came as a massive shock to Colt, who had already manufactured some 27,900 launchers up to that point, most of which were in Vietnam.[3]

The Grenade Launcher Attachment Development program was then announced in early 1968, attempting to find a new weapon to replace the XM148. Various companies submitted designs, including Philco-Ford, Aerojet, AAI and Colt, who submitted the CGL-5, an improved version of the CGL-4 designed by Henry A. Into, and offered to the Army a batch of 20 launchers for no cost at all. Despite the offer the Army rejected the CGL-5 outright, with the winning design being what would eventually become the M203 grenade launcher, designed by AAI; ironically, Colt would become the main producer of the M203 in the coming years.[3]

Design Details[edit | edit source]

The CGL-4 was a striker-fired breech-loaded grenade launcher. The weapon was loaded by sliding the pistol grip forward which was attached to the barrel. The weapon featured a rather complex set of sights attached to the right of the gun. A long trigger bar protruded out the rear of the weapon and was pulled to fire the weapon. The CGL-4 featured a rear charging handle which had to be pulled in order to ready it for firing; approximately 30 pounds (14 kilograms) of force was required to charge the weapon.[3]

The CGL-4 came packaged in a cardboard box simply marked with "XM148" and the CGL-4's serial number. The inside of the box contained the CGL-4 itself, the sight assembly, mounting system and a heat shield assembly for the AR-15.[6]

Variants[edit | edit source]

CGL-5

Improved variant. Can be distinguished with a knob-shaped cocking piece.

References[edit | edit source]

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