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Colt Machine Gun
Colt Machine Gun
Colt Machine Gun
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The Colt Machine Gun or CMG was an open bolt belt-fed machine gun that fires 5.56×45mm cartridges designed by Colt Manufacturing Company in 1965.[1] Colt hastily developed the CMG-1 to complement the CAR-15, a Colt branding of the M16 rifle, so that Colt might offer both of them as an alternative to the Stoner 63 weapons system. It failed to achieve any sales, and was replaced by the Colt CMG-2, which also failed to achieve any sales. The CMG-3 was a 7.62×51mm NATO version that failed as well.

Key Information

Colt Machine Gun #1 (CMG-1)

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Though marketed together with the CAR-15, the CMG-1 had few parts in common with it. One CMG-1 used direct impingement and shared the bolt, gas tube, and other operating parts of the M16. However, other CMG-1s used gas pistons. The CMG-1s also used the M16's pistol grip, front sight block, and flash hider. Similar to the Stoner 63, the CMG-1 could be fed from either side. The rate of fire was 650 rounds per minute. Only two or three CMG-1s were ever made. Colt made them with sheet-metal stamping.

Colt offered the CMG-1 in four different versions: bipod-mounted, tripod-mounted, vehicle-mounted, or fixed mount. The 11.5 lb (5.2 kg). bipod-mounted version was marketed as a light machine gun for use by assault troops. It was the only version with a buttstock. The 12.5 lb (5.7 kg). tripod-mounted version was considered a medium machine gun. The vehicle mounted version was a pintle-mounted machine gun for use by soldiers in land vehicles. The fixed mount version was fired by a solenoid allowing for remote operation so it could be mounted in a helicopter or other aircraft.

Colt Machine Gun #2 (CMG-2)

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In 1967, Colt replaced the CMG-1 with the CMG-2. The CMG-2 abandoned any commonality with the M16 and was only available as a bipod-mounted full-automatic-fire-only light machine gun with a vertical foregrip. The CMG-2 was gas-piston operated, but used a modified M16 bolt. The firing pin was double-sided, so it could be reversed if it was damaged or broken. The extractor was machined into the bolt and ejected spent rounds down through the vestigial magazine well. The fixed plastic stock was built into the back of the bolt-carrier group.

The CMG-2's barrel was detachable and had a folding handle, so an overheated barrel could be replaced in the field. The barrel had a 1:9 twist and was meant to fire an experimental 68-grain (4.4 g) bullet, designed for longer ranges than the then-standard 55-grain (3.6 g) M193 bullet. Unlike the M60 machine gun then in use in the Vietnam War, which had its bipod and gas cylinder as integral to the spare barrel, an M2 bipod was mounted over the gas plug set in the CMG-2's ventilated handguard and was locked into place by the spare barrel's gas block.

The most unusual feature was that it lacked the charging handle of the M16. The operator charged the CMG-2 by unlocking the pistol grip and then sliding it forward and back to chamber a round from the belt and cock the weapon. A flat rectangular piece of metal slid on the trigger group's rails behind the trigger mechanism to act as a dust cover and keep debris out of the weapon.

It was fed from a disintegrating metal belt using Stoner's proprietary S-63 BRW links. The S-63 BRW was a scaled-down 5.56mm NATO version of the M-60's M13 metal links for the 7.62mm NATO cartridge. Belted ammo was contained in a 150-round Stoner green or black plastic drum that mounted on the left-hand side of the weapon.

Colt submitted a buttstock-less short-barreled CMG-2 to the Navy SEALs. The Navy classified the CMG-2 as the EX 27 Mod 0 machine gun but they ultimately chose the Stoner 63 MK23 Mod 0 Commando instead. The CMG-2 never left the prototype phase and Colt ceased development in 1969.

Colt Machine Gun #3 (CMG-3)

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A version chambered in 7.62 mm was made in the early 1970s. Only a limited number were manufactured, estimated to be around 5, with 2 remaining in existence.[2]

See also

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References

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Bibliography

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Colt Machine Gun

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The Colt–Browning M1895, commonly known as the or "Potato Digger," is an air-cooled, belt-fed, gas-operated designed by American inventor John Moses and manufactured by Colt's Patent Fire Arms Manufacturing Company beginning in 1895. It was the first successful gas-operated adopted for , utilizing a distinctive downward-swinging actuated by gases to cycle the action, which earned it the nickname from its resemblance to a potato-digging tool. Chambered primarily in the cartridge (with later variants in , , 7mm Mauser, and ), it weighed approximately 36 pounds with its tripod mount and achieved a cyclic of 400 to 600 rounds per minute. Browning's design originated from patents filed in 1890 by him and his brother Matthew Sandefur Browning, with initial prototypes tested by the in 1895, leading to an order for around 200 units for shipboard and expeditionary use. Although not formally adopted by the U.S. Army due to concerns over reliability and overheating during sustained fire, the M1895 saw early combat deployment by the and in the Spanish-American War of 1898, including actions in and the , where it provided suppressive fire from naval vessels and shore positions. Its lightweight construction—compared to water-cooled contemporaries like the —allowed for horse-drawn or saddle-mounted portability, making it suitable for mobile cavalry and infantry support. The weapon gained broader international adoption, with the British Army purchasing units for use in the Second Boer War (1899–1902), where Canadian forces, including the Royal Canadian Dragoons under Lieutenant-Colonel François-Louis Lessard, employed it effectively in mounted infantry roles. During the Philippine-American War (1899–1902) and the Boxer Rebellion (1900), U.S. forces continued its use, while exports reached Russia (approximately 15,000 units), Italy, Belgium, and others for conflicts including the Russo-Japanese War (1904–1905) and the Mexican Revolution (1910–1920). In World War I, the M1895 served in limited capacities with U.S., Canadian, and Allied expeditionary forces starting in 1914, often as a training or secondary weapon, though it was largely supplanted by more reliable designs like the Browning M1917 water-cooled gun, which evolved from similar Browning principles and was mass-produced by Colt. Postwar, variants of the M1895 persisted into the and , including use by the British and U.S. for shore patrols, as well as adaptations like the Model 1918 aircraft gun for synchronized aerial firing. Despite criticisms for its mechanical fragility and tendency to jam in dusty conditions, the Colt Machine Gun marked a pivotal advancement in automatic weaponry, influencing subsequent Browning designs that defined U.S. military small arms through three major wars.

Overview

History and Development

In 1965, Colt Manufacturing Company initiated the development of a light machine gun chambered in 5.56×45mm NATO, intended to serve as a squad automatic weapon complementing the M16 rifle recently adopted by U.S. forces. This project was driven by growing military interest in lightweight, high-mobility support weapons to enhance infantry firepower, particularly amid the escalating demands of the Vietnam War where troops required reliable automatic fire without the burden of heavier 7.62mm machine guns like the M60. The early phase focused on prototyping the CMG-1, an open-bolt, belt-fed design that incorporated M16-compatible components for logistical synergy, with initial models produced in limited numbers around 1965–1966. By 1967, Colt shifted to the improved CMG-2 prototype, incorporating a gas-piston operating system and features like a quick-change barrel to address reliability issues in sustained fire scenarios, with approximately 27–30 units built for testing during 1967–1968. These iterative improvements were influenced by the need for weapons that could provide in jungle environments, drawing conceptual inspiration from modular systems like the contemporary without direct adoption of its components. In 1969, Colt submitted CMG-2 prototypes for U.S. military evaluation, including trials with Navy SEAL teams seeking a lightweight for , though it ultimately lost to the in competition. Development continued into the early , culminating in the CMG-3 variant refined by , which shifted to for broader compatibility but saw only five units produced due to persistent challenges in durability and military adoption. The Vietnam War's emphasis on portable firepower shaped these milestones, pushing Colt to prioritize reduced weight—around 12 pounds for the 5.56mm models—and ease of maintenance, though the project ended without widespread deployment.

Design Principles

The Colt Machine Gun (CMG) series was engineered with a philosophy, drawing inspiration from the system's adaptability, to enable configurable roles as a while emphasizing sustained automatic fire. This approach allowed for interchangeable components such as mounting systems (bipod, tripod, vehicle, or coaxial) and shared elements with the AR-15/M16 family, including the , front sight block, and flash hider, promoting logistical compatibility within U.S. forces. Unlike the broader multi-role modularity of the , the CMG prioritized optimization for belt-fed automatic operation, with provisions for left- or right-side feeding and potential short-stroke gas piston variants to enhance versatility in combat scenarios. A core principle was lightweight construction to enhance mobility, achieved through extensive use of stamped for the receiver and aluminum alloys for guide rails and select structural elements, resulting in a bipod-mounted configuration weighing approximately 11.5 to 12 pounds unloaded. This targeted weight under 12 pounds for the standard bipod version reflected the U.S. military push for portable squad automatic weapons, contrasting heavier predecessors like the M60. The design's emphasis on simplicity and ruggedness facilitated field maintenance, with straight-line construction minimizing muzzle climb during full-automatic fire. To support prolonged engagement, the CMG incorporated a quick-change barrel system, enabling rapid replacement to mitigate overheating during sustained bursts, paired with a cyclic rate of 650 rounds per minute for controlled, effective fire. Barrels measured 20 inches with button , balancing and heat dissipation. This feature, combined with air-cooled operation, allowed the weapon to maintain reliability without excessive weight penalties. The series achieved cartridge parity with the by chambering the round (CMG-1 and CMG-2), but was optimized for an experimental 68-grain bullet with a 1:9 twist, which limited full ammunition logistics simplification as it was not compatible with the standard M193 55-grain cartridge and required a separate supply. This partial commonality aligned with the era's efforts but impacted operational integration into M16-equipped squads.

Technical Specifications

Operating System

The Colt–Browning M1895 utilizes a gas-operated mechanism employing a distinctive downward-swinging , known as the "potato digger" action, which cycles the action from a closed-bolt configuration. In operation, propellant gases are diverted through a port in the barrel to a located below it, where they impinge on the attached to the bolt. This causes the lever to swing downward and rearward, unlocking and retracting the bolt to extract and eject the spent cartridge case, while compressing a spring. As the gases dissipate, the spring drives the bolt forward, stripping the next round from the belt, chambering it, and locking the bolt closed before firing. The closed-bolt design allows for improved accuracy in semi-automatic-like bursts but requires careful to prevent issues during sustained fire. The weapon features a fixed barrel with no quick-change option in early models, though later variants incorporated improvements for reliability. The M1895 lacks selective fire modes, operating solely in full-automatic, with a cyclic of approximately 400 to 450 rounds per minute. Safety is provided by a manual safety lever, and the overall is 41 inches (104 cm), with a barrel of 28 inches (71 cm). The air-cooled barrel, weighing about 35 pounds (16 kg) for the gun alone, contributes to portability compared to water-cooled designs, though the complete system with weighs around 90 pounds (41 kg).

Ammunition and Feeding

The Colt–Browning M1895 is chambered primarily in the cartridge for U.S. service, with variants produced in , , 7mm Mauser, and to meet export demands. It employs a belt-feeding system using non-disintegrating fabric belts, typically holding 250 rounds, fed from the left side via a receiver-mounted . This allows for continuous fire without the need for reloading magazines, suitable for suppressive roles. The cyclic rate of to rounds per minute balances sustained fire with barrel cooling, as the low rate prevents excessive overheating in the air-cooled . Depending on the cartridge, muzzle ranges from approximately 2,000 feet per second () to 2,800 feet per second (), achieving an effective range of 600 to 1,000 meters. is managed through the weight of the system and optional mounts, with minimal due to the inline .

Variants

The Colt–Browning M1895 was produced in several s to meet various military requirements. The primary version was chambered in (7.62×56mmR), as adopted by the U.S. Navy and for early U.S. Army trials. Later adaptations included (7.62×63mm) for U.S. use, (6×55mmR) for naval applications, 7mm (7×57mm) for export, (7.7×56mmR) for British and Commonwealth forces, and 7.62×54mmR for Russian contracts. These variants maintained the core gas-operated, belt-fed design but required adjustments to the barrel and bolt for compatibility.

Colt Model 1914

The Colt Model 1914 was a commercial modification of the M1895, featuring a detachable finned barrel for improved cooling and easier maintenance. Produced during , it was chambered primarily in for U.S. training and export markets, as well as and . Approximately several thousand were manufactured, with sales to Allied nations including , , , and Britain.

Marlin Models 1917 and 1918

Due to high demand during , Colt licensed production to Marlin Arms Corporation, resulting in the Marlin Model 1917 and Model 1918. These variants incorporated improvements such as a , enhanced sights, and an access door for clearing malfunctions. The Model 1917 was used for ground training and support, with about 2,500 units produced for the U.S. Army in 1917. The Model 1918 was optimized for mounting, featuring a linear gas instead of the original swinging lever and an aluminum radiator for weight reduction. Around 38,000 Model 1918 units were made for U.S. , though they saw limited combat use due to synchronization issues with propellers. Both models retained the air-cooled, belt-fed mechanism and were chambered in .

Testing and Deployment

Military Trials

The Colt Machine Gun prototypes, particularly the CMG-1 and CMG-2 variants, underwent evaluation by U.S. military branches in the late and early as part of efforts to identify a to support the in squad-level operations. The CMG-2 was submitted for competition in the U.S. SEALs' light machine gun selection process, where it was tested against the system and ultimately placed second, leading to no adoption by the SEALs. Field testing of the CMG-2 occurred in in 1970 by U.S. SEALs, demonstrating initial advantages in mobility and controllability during combat scenarios, though the weapon faced challenges in reliability under harsh environmental conditions. Limited evaluations by Marine Corps Recon teams also explored the CMG-2 as an alternative to existing automatic weapons, but these did not result in . The designs were assessed on factors including weight, integration with M16 logistics, and overall durability, with the Colt prototypes receiving moderate marks for delivery but lower scores for sustained reliability.

Operational Limitations

The Colt Machine Gun series, particularly the CMG-2 and CMG-3 variants, exhibited significant reliability shortcomings during military evaluations in the late 1960s and early 1970s. The CMG-3 suffered from receiver cracking at the front after approximately 35,000 rounds of sustained fire, far below the U.S. Navy's requirement of 100,000 rounds for operational durability. This failure mode was attributed to the design's scaling from the lighter 5.56mm CMG-2 to the more powerful , leading to structural stress under prolonged use. Similarly, the CMG-2 demonstrated inadequate range and in U.S. trials conducted in using 68-grain ammunition, resulting in frequent performance inconsistencies that prevented its adoption. Ergonomic limitations further hampered the weapon's practicality in field conditions. The CMG-2's belt-fed , holding 150 rounds in disintegrating links, proved awkward to reload under combat scenarios, complicating rapid resupply during mobile operations. Additionally, its charging mechanism—a sliding rear —introduced handling inefficiencies compared to more conventional designs, reducing overall user effectiveness in dynamic environments. Logistically, while the CMG-1 incorporated some M16-compatible components such as the , sight block, and flash hider to leverage existing supply chains, the series' specialized belt-feeding system relied on proprietary elements like Stoner 63-derived links, necessitating separate maintenance and procurement streams. This offset any potential commonality benefits, as the belt-feed assembly's complexity increased vulnerability to field failures and logistical burdens in military deployments.

Legacy and Impact

Influence on Firearm Design

The Colt Machine Gun (CMG) project, particularly its emphasis on lightweight, 5.56mm belt-fed designs with features like quick-change barrels, contributed to the conceptual foundations of subsequent U.S. squad automatic weapons by highlighting the need for portable, high-volume fire support integrated with rifle systems. Although the CMG itself was not adopted, its development in the late 1960s informed the U.S. Army's Squad Automatic Weapon (SAW) program initiated in 1972, which sought to address the limitations of heavier machine guns like the M60 in Vietnam-era infantry tactics. Key technical elements from the CMG-2, such as the quick-removable barrel to manage heat during sustained fire, were echoed in the (adopted as the M249 SAW in 1984), which prioritized similar rapid barrel changes for reliability in squad-level suppression. This design choice enabled the M249 to deliver 750-1,000 rounds per minute while weighing just 17 pounds unloaded, marking a direct evolution from earlier 5.56mm LMG experiments like the CMG toward lighter, more maneuverable support weapons. The CMG's open-bolt, belt-fed mechanism also tested feeding systems that influenced the M249's dual-feed capability from belts or magazines, enhancing tactical flexibility. The project's modular aspects, including the CMG-1's compatibility with AR-15/M16 components like pistol grips and sights, foreshadowed broader trends in interchangeable weapon systems, paving the way for platforms like the (adopted in 2009) that allow caliber and role swaps via common receivers and rails. By demonstrating the viability of shared parts across rifles and automatics, the CMG reinforced engineering principles for multi-role modularity seen in the (2010s), where barrels and uppers can be exchanged without tools. Doctrinally, the CMG efforts aligned with the post-Vietnam U.S. military pivot toward lighter support, influencing programs like the (SPIW, 1960s-1970s) and (ACR, 1980s) by underscoring the demand for reduced-weight automatics to boost squad mobility and firepower density. This shift, driven by Vietnam lessons on , led to the SAW program's focus on one automatic per fire team, embedding the CMG's lightweight ethos into modern doctrine. Technically, refinements in the CMG-2's gas-piston operating system—abandoning for better reliability under heavy use—were adopted in civilian AR-15 belt-fed conversions, such as those using piston uppers for sustained fire without fouling the bolt carrier. These adaptations, seen in kits like the Ares Defense Shrike (2000s), extend the AR platform's versatility while mitigating overheating issues first explored in the CMG.

Modern Collectibility

The Colt Machine Guns, particularly the CMG-1 and CMG-2 prototypes, are exceedingly rare artifacts, with only a handful produced during their developmental phases in the and early , and fewer than a dozen known surviving examples across variants held in private collections or institutions such as the Institute of Technology. The CMG-3 variant is even scarcer, with just five units ever manufactured and only two confirmed to remain in existence today. These firearms' limited production and historical obscurity contribute to their status as prized items among serious collectors of experimental weaponry. Under U.S. law, all Colt CMG models are classified as (NFA) items due to their full-automatic capability, necessitating ATF registration, a $200 tax stamp for transfers, and compliance with strict federal regulations for possession and ownership. Transferable examples, those registered prior to the Hughes ban on new civilian machine guns, command premium prices at , often ranging from $30,000 to over $100,000 depending on condition and provenance; for instance, a fully transferable CMG-3 sold for $120,000 at a 2015 James D. Julia . Demilled (deactivated) versions, which cannot fire, are more accessible to non-NFA collectors but still fetch significant sums, reflecting the growing interest in 1960s-era firearm innovation amid broader nostalgia for Cold War-era designs. Restoration efforts face substantial hurdles owing to the scarcity of original parts, as Colt ceased production decades ago and no official spares were mass-produced. Enthusiasts have turned to modern solutions like 3D-printed accessories for non-critical components, such as grips or cheek risers, to preserve functionality in surviving examples without compromising authenticity. This combination of rarity, regulatory complexity, and preservation challenges underscores the Colt Machine Gun's niche appeal in the contemporary collectibles market as of 2025.

References

  1. https://www.americanrifleman.org/content/the-colt-1895-america-s-first-browning-machine-gun/
  2. https://www.warmuseum.ca/cwm/exhibitions/boer/coltmachinegun_e.html
  3. https://www.mainememory.net/sitebuilder/site/2662/slideshow/1616/display?use_mmn=1&format=slideshow&prev_object_id=4282&prev_object=page&slide_num=2
  4. https://www.spanamwar.com/Coltmachinegun.htm
  5. https://qmmuseum.army.mil/research/secondary-sources/books/WWI/AmericasMunitions1917-18.pdf
  6. https://www.historicalfirearms.info/post/101960250566/colt-cmg-series-the-colt-machine-gun-project-was
  7. https://www.sandboxx.us/news/exploring-the-cmg-colts-forgotten-machine-gun/
  8. https://www.forgottenweapons.com/colt-cmg-2-light-machine-gun-video-and-manual/
  9. https://guns.fandom.com/wiki/M1895_Colt_Browning_machine_gun
  10. https://www.americanrifleman.org/content/this-old-gun-colt-model-1895-machine-gun/
  11. https://modernfirearms.net/en/machineguns/u-s-a-machineguns/colt-browning-m1895-eng/
  12. https://www.militaryfactory.com/smallarms/detail.php?smallarms_id=785
  13. https://www.imfdb.org/wiki/Colt_1895_Automatic_Machine_Gun
  14. https://www.forgottenweapons.com/potato-digger-at-war-marlin-model-1917-machine-gun/
  15. https://airandspace.si.edu/multimedia-gallery/fc0e002827482002jpg
  16. https://www.forgottenweapons.com/light-machine-guns/colt-cmg-2/
  17. https://smallarmsreview.com/behind-the-vault-door-the-naval-historic-centers-weapons-collection/
  18. https://www.forgottenweapons.com/shooting-a-colt-cmg-3-at-james-d-julia/
  19. https://michellawyers.com/wp-content/uploads/2020/01/2020-01-27-Appellants-Excerpts-of-Record-Vol.-IX.pdf
  20. https://www.thefirearmblog.com/blog/us-army-saw-program-hk23a1-and-hk21a1-44820274
  21. https://www.machinegunboards.com/forums/index.php?/profile/257834-mg08/content/page/20/&type=forums_topic_post
  22. https://www.rockislandauction.com/riac-blog/nfa-machine-guns-and-the-collectors-market/
  23. https://www.reddit.com/r/RetroAR/comments/1j6wv76/i_finished_designing_a_3d_printed_car15_cheek/
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