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The Famous CAR-15's Path to Modern Combat Rifles

The Colt CAR-15 was a lightweight and controllable carbine version of the M16A1 first used in combat in Vietnam and was a coveted PDW by Army aircrews shot down and in close combat.

The Famous CAR-15's Path to Modern Combat Rifles

The Colt CAR-15 was a coveted personal defense weapon among Army aircrews during the Vietnam War. There never seemed enough of the stubby little guns to go around. (Firearms News photo)

It was the summer of 1969, and Southeast Asia was an understudy for hell. LT Hugh Mills had launched that morning along with his gunner Jim Parker in an OH-6A Loach observation helicopter as half of a hunter-killer pink team. Alongside a G-model AH-1 Cobra flying top cover, they were tasked with clearing the route for a supply convoy on a length of highway called Thunder Road. LT Mills’ bit involved flying low and slow just above the ground in an effort at teasing out ambushes and booby traps before the trucks arrived. It was stressful, dangerous work, but these low-level security sweeps ultimately saved countless American lives. While sweeping an area supposedly cleared of VC, Mills and his gunner were suddenly hammered by a well-hidden .50-caliber machinegun. A big half-inch round punched through the leading edge of one rotor blade about four feet from the tip. This left the entire rotor system out of balance and failing. The resulting vibration was mind numbing.

Vietnam-era Historical CAR-15 Combat rifle
From top to bottom we have the Colt CAR-15, the Chicom Type 56 AK-47, and the M16A1. (Firearms News photo)

Mills’ Loach was going down hard. That decision had been made by the enemy. All that remained was to work through the details. In a remarkably rarefied bit of pilotage, LT Mills guided his stricken machine onto a fairly flat spot in a rice paddy. Mill’s gunner split his chin badly on the front sight of his M-60, but both men were otherwise unhurt. In moments, the two Americans were clear of the wreckage and taking stock. Mill’s gunner had recovered his M60 machinegun along with a seven-foot belt of linked 7.62x51mm ammo. LT Mills grabbed his CAR-15 assault rifle and a bandolier full of 20-round magazines. Mills had a single 30-round box he kept in his weapon. Just then, the world veritably exploded with AK-47 fire.

Vietnam-era Historical CAR-15 Combat rifle
The XM177E2 saw widespread use among special operators like this 1st Cav LRRP team (top right). The Hughes OH-6A Light Observation Helicopter or Loach was an exceptionally capable and crash-worthy machine. It was roundly adored by its pilots (bottom right). (Public domain) 

Two VC soldiers emerged from a tree line some 175 yards distant and began peppering the paddy with their AK47’s. In response, Parker hosed the area with a long burst from his M-60. LT Mills sighted his stubby little CAR-15, thumbed the selector to full auto, and torqued down on the trigger. The force of the impacting rounds threw the two VC backwards into the muck. What followed was a roiling gunfight as the remaining VC tried to maneuver in close, and the two downed aviators fought for their very lives. Parker retrieved more ammunition from the downed aircraft, while Mills fired burst after burst from his CAR-15 toward the attacking VC. Their supporting Cobra made gun and rocket runs on the hostile tree line until it ran out of ordnance.                                                      

Just when things seemed bleakest, a lone UH-1H Huey swept over the rice paddy and came to a smart hover some twenty feet from where the two downed aircrewmen were crouching behind the paddy dike. Both men slogged through thigh-deep muck to throw themselves onto the aircraft. The helicopter that swept the men to safety was the Infantry Brigade CO’s command and control bird.  The following day, Mills and Parker were back in the same area in a fresh aircraft scouting the carnage for useful intelligence. Thanks to the deft wielding of their M-60 and CAR-15, they had held the enemy at bay long enough to be rescued. That stubby little assault rifle was destined to go on to achieve even greater things.

Origin Story

Vietnam-era Historical CAR-15 Combat rifle comparison rifles
The ultimate answer to the Army’s need for a carbine-sized version of the M-16A1 was the XM177E2. The XM177E2 was best known among aviators and Special Forces troops in theater in Vietnam. (Firearms News photo)

Vietnam was the Wild West when it came to military firearms. We started the war with the heavy 7.62x51mm M-14 battle rifle. However, it soon became obvious that American grunts needed something lighter and more maneuverable for operations in the restricted confines of the Southeast Asian jungles. The end result was the M-16. The M16 was a 5.56x45mm development of the previous 7.62x51mm AR-10. That origin story should be foundational dogma to most anyone gripping this hallowed tome. At less than 40 inches long, and less than 6.5 pounds, the M16 offered controllable selective fire firepower in a package that was easy to carry, pack, and run. However, Uncle Sam still had need of something smaller for dog handlers, SF operators, aviators, and the like. In previous wars, this role had been filled by pistol-caliber submachine guns and the M1 carbine.

The Thompson family of SMG’s along with the M3 Grease Gun and the German MP-40 would be typical examples. These weapons were indeed handy and maneuverable, but their pistol chambering limited both range and downrange thump. Additionally, running a caliber other than the standard rifle cartridge on a real-deal fluid battlefield substantially complicated resupply. This drove the Army to press industry to create a hybrid stubby assault rifle that combined the modest size of the SMG with the power of the M16. The ultimate result was the XM177E2. When I was a kid growing up in the 1970’s, I was simply smitten with this thing. Interestingly, unlike most military weapons systems, the nomenclature and development were terribly convoluted affairs. There were influences both commercial and military, but the end result paved the way for the highly refined combat rifles our troops are packing downrange even today.

Vietnam-era Historical CAR-15 Combat rifle comparison rifles
The 1950’s-era ArmaLite AR-10 (middle) eventually begat a sprawling family of infantry weapons. The earliest M16 rifles (bottom) lacked a forward assist and sported an open three- pronged flash suppressor. (Firearms News photo)

The starting point for this remarkable voyage was actually a prototype “tanker” version of the AR-15 first developed in 1959. This stubby little gun was only 26 inches long when fully collapsed. As the barrel was too short to accommodate a bayonet, its lug was deleted. The first serious effort at creating a subgun-sized production version of the M-16 was the Colt Model 607 developed in 1965. This curious beast looked like you took an early model M-16 and crushed it lengthwise. The weapon first sported the standard open three-prong flash suppressor (later replaced by a flash and sound “moderator”) as well as an abbreviated set of black polymer triangular handguards. The stubby solid plastic buttstock also incorporated a sliding mechanism to adjust its length. However, this buttstock design was found to be fairly unwieldy under hard use. Anyone in possession of a transferable example of this rascal is well on their way toward a decent retirement today.

Colt subsequently folded the foundational Model 607 into the CAR-15 Military Weapons System. The CAR-15 MWS was a family of firearms all based upon a common M-16 receiver. The AR in the term AR-15 was short for ArmaLite Rifle. CAR-15 stood for “Colt Automatic Rifle.” This was a marketing gimmick intended to enhance brand recognition for Colt and further distance the gun from its ArmaLite origins. The resulting weapon was also commonly referred to as the Colt Commando. Colt’s improved version of the Model 607 was the Model 609.

The Model 609 differed from the Model 607 in several critical ways. Colt engineer Rob Roy was tasked to redesign the buttstock. His brainchild was a rubber-coated aluminum sliding version that looked quite similar to the current M4 stocks of today. Colt later fielded a polymer version of the stock that looked about the same in dim light but were easier to make. The handguards were replaced with interchangeable round versions that fit top and bottom. This ended up being a significant improvement over the triangular left and right-handed sort used on the M16. Not only were the round versions heartier, as they were interchangeable it also eased supply challenges.

Vietnam-era Historical CAR-15 Combat rifle
The collapsible stock Robert Roy designed back in 1966 went on to inspire all of the M4 stocks in use today. The step on the XM177E2 flash suppressor (top left) was designed to accept a 40mm grenade launcher. The concept of interchangeable round handguards (top right), like those used on the XM177-series of rifles, were ultimately adapted for use in the M-16A2. Eugene Stoner actually offered round handguards for the full-size M16 in 1965, but he was too forward thinking at the time. (Firearms News photo)

Original Model 609 barrels were 10 inches long and topped with a 4.25-inch sound moderator. Cutting the tube in half (the standard M-16 barrel is 20 inches long) created an ungodly muzzle flash and racket. The addition of the moderator made such stuff sort-of tolerable. Interestingly, while this moderator in no way silences the weapon (just reduces sound report down to about the level of a full-sized M16), BATF still considers original examples to be NFA items demanding registration. The Army bought its first lot of 2,815 Model 609s in the summer of 1966. These weapons were type-classified as the XM177E1 and were supposed to come with seven thirty-round magazines apiece. However, Colt engineers were unable to perfect the extended magazines in time to meet delivery, so they were shipped with standard 20-round boxes.

In 1967, due to cycling issues of the shorter barrel, the barrel was stretched out to 11.5 inches while retaining the sound moderator. This weapon was christened the Model 629 in Colt parlance and the XM177E2 for Uncle Sam. The Army purchased 510 of these little rifles for use by Military Assistance Command, Vietnam-Studies and Observations Group (MACV-SOG) in April of 1967. A shortage of 30-round magazines plagued the weapon throughout the war. Interestingly, SF guys often bought 30-round mags with their own money out of the back of gun magazines for use in their combat weapons since the commercial semiauto Colt AR-15 was readily available, along with a few accessories. Formal production of the XM177-family of weapons wrapped up in 1970. There were ultimately scads of different subvariants, each of which earned its own designation. The Model 609 Commando had a forward assist, while the Model 610 did not. There was even a Model 610B equipped with a four-position selector. The US Air Force bought the Model 610 without the forward assist as the GAU-5/A Submachine Gun. When I worked with Air Force personnel back when I was an Army Aviator in the 1990’s, their sundry carbines all lacked the forward assist devices.

Vietnam-era Historical CAR-15 Combat rifle
The Colt Model 607 (top), the CAR-15’s “daddy.” The M-14 (middle), superb battle rifle that it was, remained ill-suited for service in the constricted confines of the Vietnam jungles. The Colt Model 653 (bottom) was a transitional form between the XM177E2 and the M4 carbines of today. (Firearms News photo)

Amidst the post-Vietnam malaise that infected the US military, it became obvious that there yet still remained a need for a stubbier version of the M16. In the early 1970’s, Colt developed a variant of the XM177E2 that incorporated a thin-profile 14.5-inch barrel topped with a standard birdcage flash suppressor. As it forewent the sound moderator, this weapon had the same overall length as the previous XM177E2 while offering improved ballistics. There were several different versions produced but only the Model 653 was purchased in any quantity by the US military. Curiously, both Malaysia and the Philippines bought these weapons as well. This is the reason the carbines carried in the Oliver Stone movie Platoon sported the pencil-profile 14.5-inch barrels. The film was shot in the Philippines and used Filipino military weapons in the production.


In the early 1980’s, Colt developed the M16A2 for the US Marine Corps. The M16A2 was a pound heavier than the M-16A1 and included an improved sighting system, heavier barrel, redesigned pistol grip, and burst limiter along with a few other minor tweaks. Over time these upgrades were folded into the CAR-15 chassis along with the familiar stepped 14.5-inch barrel to become the M4. The barrel step was included to accommodate the M203 grenade launcher. The subsequent M4A1 was essentially the same weapon with a heavier barrel and full auto fire selector.

Trigger Time

Vietnam-era Historical CAR-15 Combat rifle
The CAR-15 is a joy on the range. Lightweight, compact, and maneuverable, the little rifle is easy to tote and fast in action. (Firearms News photo)

I bought my stripped 11.5-inch CAR-15 barrel used at a gun show back in the 1980’s. It was already shot out when I found it. Now, untold thousands of full auto rounds later that problem hasn’t gotten any better. I have actually run this thing so hard with a Brocal .22 conversion device installed that I’ve had to hammer accumulated lead out of the bore with an old cleaning rod. As such, it seemed unfair to make any real assessment of the weapon with that kind of blighted pedigree. The answer was an XM177E2 clone from Troy Industries.

Troy made these guns in limited runs some years ago. Interestingly, I tripped over a replica of the Israeli Mekut’zar carbine that was built using a Troy XM177E2 as a foundation on GunBroker. The original builder had set the Troy upper aside but included it with the package when he sold me the gun. The Troy version is a splendid recreation right down to the receiver markings and the absent bayonet lug. However, the flash suppressor does not moderate the sound, and it is pinned in place to create a legal overall length of sixteen inches. My first impression was how lightweight and maneuverable this gun was before we started hanging so much crap all over it. Packing the XM177E2 is positively ethereal compared to more modern tricked-out fare. The iron sights reflected the state of the art at the time and were both simple and effective. Recoil was negligible, and follow-up shots were a joy. Magazine changes were no different from those of your typical M4.

Vietnam-era Historical CAR-15 Combat rifle
These 25-meter proofing groups (left) were fired off-hand over open sights from a simple rest. The M4-family of carbines (top right) soldiers on downrange as I type these words. This lightweight and maneuverable combat rifle traces its origins back to the Vietnam-era CAR-15. (Firearms News photo)

My eyes are 56 years old. Shooting most anything at long distances over iron sights transforms it into an area weapon system. However, I shoot about as well with the XM177E2 as I do with an M-16A1. The stubby tube does indeed drop the muzzle velocity appreciably, but at close to mid ranges the weapon remains quite potent. CAR-15’s were always in short supply in theater in Vietnam. I can recommend without reservation both Low Level Hell by Hugh Mills and Secret Commandos by John Plaster for some superlative down-in-the-dirt observations about small arms in Vietnam. Mills explores the concept from the perspective of an aviator packing weapons for personal defense. Plaster’s point of view is that of a special operator on covert missions deep in hostile territory. Both books are available on Amazon.

Interestingly, Major Plaster made a fascinating observation concerning the noise and muzzle chaos of the XM177E2 that I never would have suspected. Early on during his time in MACV-SOG, there was a shortage of carbines. He therefore opted to carry a sound-suppressed 9mm Swedish K submachine gun. This would seem the ideal tool for prisoner snatches and similar clandestine operations. However, when things devolved into a full-bore gunfight, the lack of noise became a serious liability. When Plaster and his comrades were trying to establish fire superiority, the relative dearth of muzzle racket tended to encourage the NVA to press an attack. By contrast, opening up at close range with these stubby cacophonous CAR-15’s would help put the bad guys’ heads down.

The CAR-15 was a fascinating steppingstone to the modern combat rifles in use today. Certain attributes of the design are literally unchanged, while other stuff like forearm rails and electro-optics would have been unimaginable back in 1967. Regardless, exercising one of these stubby little rifles on the range yields insights into both where we’ve been as well as the shape of things to come.

Vietnam-era Historical CAR-15 Combat rifle Accuracy Data

Vietnam-Era XM177E2 CAR-15 Carbine Specs

  • Type: Gas-operated, rotating bolt, direct impingement
  • Caliber: 5.56x45mm
  • Weight: 5.35 lbs. 
  • Overall Length: 32.5/29.8 in. (extended/retracted) 
  • Barrel Length: 11.5 in. 
  • Feed: 20/30 rd. box magazines
  • Cyclic Rate: 750 rpm
  • Sights: Protected Post front/Flip Rear peep
  • Manufacturer: Colt (discontinued) 

About the Author

Will is a mechanical engineer who flew UH1H, OH58A/C, CH47D and AH1S aircraft as an Army Aviator. He is airborne and scuba qualified and summited Mount McKinley, Alaska, six times…at the controls of an Army helicopter. After eight years in the Regular Army, Major Dabbs attended medical school. He works in his urgent care clinic, shares a business building precision rifles and sound suppressors, and has written for the gun press since 1989.

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