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M3 submachine gun

The M3 submachine gun, officially the United States Submachine Gun, Caliber .45, M3, is an air-cooled, blowback-operated, magazine-fed automatic firearm designed for close-quarters combat and issued primarily to vehicle crews, tankers, and support personnel in the U.S. military.^[1] Adopted by the U.S. Army Ordnance Department on December 12, 1942, it was conceived as a rugged, low-cost replacement for the more expensive Thompson submachine gun, utilizing stamped sheet metal construction with only 73 parts to facilitate mass production during World War II.^[2] Weighing 8.15 pounds empty and measuring 22.0 inches long with the wire stock collapsed, the M3 fires .45 ACP cartridges from a 30-round detachable box magazine at a cyclic rate of 400–450 rounds per minute, achieving a muzzle velocity of approximately 920 feet per second and an effective range of up to 100 yards.^[3] Its utilitarian appearance, resembling a mechanic's grease gun, earned it the enduring nickname "Grease Gun."^[2] Developed in 1942 by engineers George J. Hyde and Frederick W. Sampson at the U.S. Army Ordnance Department, the M3 drew inspiration from economical foreign designs like the British Sten gun and German MP40, meeting strict requirements for durability, simplicity, and compatibility with existing .45-caliber ammunition.^[2] Production was assigned to the Guide Lamp Division of General Motors in Anderson, Indiana, with initial output beginning in 1943; a total of 606,694 M3 variants were manufactured by the war's end, at a unit cost of about $20.94, compared to over $200 for the Thompson.^[2] The weapon's telescoping wire stock doubled as a cleaning rod and barrel-removal wrench, while early models featured a side-mounted cocking handle, though issues like frame warping and magazine jamming prompted refinements.^[1] In December 1944, the improved M3A1 variant was adopted, eliminating the fragile cocking handle in favor of a rear bolt slot for charging, adding an ejection port cover, and incorporating a pistol grip oil reservoir for maintenance; it weighed slightly less at 7.95 pounds and saw production of 48,669 units.^[3] The M3 entered combat during the D-Day landings on June 6, 1944, issued to paratroopers of the 82nd and 101st Airborne Divisions, and remained the U.S. Army's primary submachine gun through the Korean War, Vietnam War, and into the 1990s, serving also with special forces units like the OSS and Green Berets until its official retirement in 1991.^[2] Despite its automatic-only fire mode and simple mechanical safety via the ejection port cover that locks the bolt when closed—the M3's reliability in harsh conditions and adaptability, including rare 9mm conversions, solidified its legacy as one of the longest-serving U.S. small arms.^[1]

Development and Production

Design Origins

During World War II, the U.S. military faced increasing demands for submachine guns as part of its rapid rearmament efforts, particularly for compact weapons suitable for paratroopers, tank crews, and other specialized roles. The Thompson submachine gun, while reliable and effective, proved too expensive and resource-intensive to produce in sufficient quantities, with wartime unit costs around $45 after simplifications, exacerbating production bottlenecks amid the 1942 mobilization surge. To address this, the Army Ordnance Department initiated a program in 1940 to develop a cheaper alternative that could fire .45-caliber ammunition at a controlled rate of 500 rounds per minute or less, while maintaining accuracy—such as hitting a 6-foot target at 50 yards at least 90 out of 100 times—and using minimal critical materials for mass production.^[2] The design effort was led by Colonel René R. Studler of the Army Ordnance Technical Committee, who enlisted firearms designer George J. Hyde and Frederick W. Sampson, chief engineer at General Motors' Inland Division, to create a simplified weapon. Hyde, a German immigrant with prior experience in submachine gun prototypes, collaborated with Sampson to prioritize stamped and pressed sheet metal construction over the Thompson's machined components, reducing the total parts count to 73—mostly spot-welded or riveted for ease of assembly—and targeting a production cost of about $20 per unit. This approach aimed to enable high-volume output using automotive manufacturing techniques, with only the bolt and barrel requiring precision machining, allowing the Inland Division (later shifted to GM's Guide Lamp Division) to adapt existing assembly lines. The first prototypes, designated T15 with an all-metal wire stock and later refined as the T20 in automatic-only configuration, were completed in mid-1942.^[2]^[4] Early testing of five T20 prototypes at Aberdeen Proving Ground in November 1942 demonstrated strong performance under simulated combat conditions, including mud, dust, and reliability trials where it outperformed other candidates and even a control Thompson in some metrics, such as 97 hits out of 100 on a target at 50 yards. Army Ordnance provided feedback on minor issues like the cocking handle and dust cover, leading to quick iterations that resolved these without major redesigns. Based on these results, the weapon was recommended for adoption and officially standardized as the United States Submachine Gun, Caliber .45, M3 on December 12, 1942, marking a swift six-month development cycle from concept to approval.^[2]^[5]^[4]

Manufacturing Process

The M3 submachine gun was primarily manufactured by the Guide Lamp Division of General Motors at its facility in Anderson, Indiana, with production commencing in May 1943.^[6] This division, known for automotive lighting components, adapted its stamping expertise to wartime small arms production under U.S. Army Ordnance contracts.^[7] The manufacturing process emphasized cost reduction through simplified construction, utilizing progressive die stamping for the receiver and most components, spot welding for assembly, and minimal machining limited to critical elements like the barrel and bolt.^[2] This approach resulted in a unit cost of approximately $20.94 in 1943, equivalent to approximately $391 in 2025 dollars after adjusting for inflation.^[8] By contrast, the contemporary Thompson M1A1 submachine gun cost over $45 per unit using more labor-intensive methods.^[7] Production ramped up quickly, reaching rates of several hundred units per day by late 1943 and peaking in 1944 amid wartime demands, with a total output of 606,694 M3 models and 15,469 M3A1 variants during World War II.^[4] Initial runs incorporated surplus parts from earlier Thompson production to accelerate output and utilize existing inventory.^[5] Manufacturing continued post-war at a reduced pace for U.S. military reserves into the early 1950s.^[9] Quality control efforts addressed early challenges, including receiver weaknesses from the telescoping bolt design and cocking slot, which prompted iterative redesigns culminating in the M3A1 variant with reinforced components and simplified operation.^[10] These adjustments improved reliability without significantly increasing costs, ensuring the weapon met Ordnance Department standards for mass issuance.^[11]

Design Details

Operating Mechanism

The M3 submachine gun utilizes a straight blowback operating system, firing from an open-bolt position without a locked breech. This design leverages the inertia of a heavy bolt to counteract chamber pressure and delay rearward movement until the bullet has exited the barrel and gas pressure has sufficiently decreased, ensuring safe extraction. The system relies on the relatively low chamber pressure of the .45 ACP cartridge, rated at a maximum of 21,000 psi by SAAMI standards, which minimizes the need for complex locking mechanisms.^[12] To initiate firing, the operator manually cocks the bolt rearward using a side-mounted lever on the M3 model (later simplified to direct finger pull on the M3A1). The bolt is retained in the rear position by a sear engaging a notch. Pulling the trigger disengages the sear, allowing dual recoil springs to propel the bolt forward. As it travels, the bolt strips the top round from a 30-round detachable box magazine, chambers it, and the fixed firing pin integral to the bolt face strikes the primer to ignite the propellant. The expanding gases then drive the bolt rearward, extracting and ejecting the spent case via a fixed ejector while compressing the springs for the next cycle. The weapon's cyclic rate is approximately 450 rounds per minute, providing controllable bursts despite full-automatic fire. It lacks a semi-automatic mode or mechanical trigger lock, relying on the dust cover and magazine removal for safe handling.^[13]^[14]^[15]^[1] Integrated safety features emphasize simplicity and mechanical reliability. The stamped-metal dust cover over the ejection port serves as the primary safety: when closed, it blocks access to the charging handle and prevents bolt movement, inhibiting accidental discharge.^[15]^[13] The mechanism's reliability stems from its engineering for wartime mass production and field endurance, featuring loose tolerances in the receiver and bolt fit—typically on the order of 0.020 to 0.030 inches of clearance—that accommodate dirt, debris, and wear without malfunctioning. Lacking a gas-operated system or intricate components, the M3 tolerates neglect and operates effectively in adverse conditions, contributing to its reputation as a robust, low-maintenance weapon.^[13]

Construction and Features

The M3 submachine gun featured a rugged, minimalist construction primarily composed of stamped and welded sheet steel, earning it the nickname "Grease Gun" due to its visual resemblance to a mechanic's lubricant applicator.^[4] The receiver and body were fabricated from pressed steel components, with only the bolt and barrel requiring machining, which contributed to its low production cost and durability in field conditions.^[2] The exterior was finished with a Parkerized coating for corrosion resistance, and the design enclosed most internal mechanisms to protect against dirt and debris.^[4] In terms of dimensions, the M3 measured 22.8 inches in overall length with the stock folded and 29.8 inches extended, with an 8-inch barrel length.^[2] It weighed 8.15 pounds empty and 10.25 pounds when loaded with a full magazine, making it lighter than its predecessor, the Thompson submachine gun.^[1] The sights were non-adjustable, consisting of a fixed front blade and a protected rear peep sight zeroed for 100 yards, prioritizing simplicity over precision.^[16] Ergonomically, the M3 utilized a pistol grip integrated into the receiver for one-handed control, paired with an optional folding wire stock that could telescope to adjust length and also served as a cleaning rod and barrel wrench.^[4] The 30-round double-stack, single-feed box magazine mounted horizontally on the left side to avoid interference with the stock, facilitating quicker reloads in prone or confined positions.^[16] Its cyclic rate of fire was approximately 450 rounds per minute, intentionally slow to enhance controllability with the heavy .45 ACP cartridge during automatic fire.^[2] Performance characteristics included a muzzle velocity of 900 feet per second and an effective range of 100 yards, suitable for close-quarters combat.^[1] The subsonic velocity of the .45 ACP round lent itself to suppression, with around 1,000 M3 variants adapted with integral suppressors for use by the Office of Strategic Services (OSS) during World War II.^[2] Standard accessories comprised a leather sling and a cylindrical oiler, while an optional flash hider could be fitted to the threaded barrel; the design omitted integral bipods or optics to maintain its compact, utilitarian profile.^[16]

Variants

M3A1

The M3A1 was adopted by the U.S. Army in December 1944 as an improved variant of the original M3 submachine gun, designed to rectify several early production flaws identified during World War II service.^[17] Key modifications included the elimination of the fragile side-mounted cocking lever and its replacement with a simple finger slot machined directly into the bolt, allowing for more reliable manual operation without the risk of breakage under field conditions.^[16] An extended ejection port with an integrated dust cover was added to better protect the internal mechanism from debris while facilitating smoother ejection, and the safety mechanism was repositioned rearward for improved accessibility.^[16] These changes addressed vulnerabilities in the M3, such as accidental slam-fires and environmental ingress, enhancing overall durability without altering the core blowback operating principle.^[2] Production of the M3A1 occurred primarily at General Motors' Guide Lamp Division in Anderson, Indiana, with 15,469 units completed by the end of World War II in 1945, following the initial M3 runs that totaled over 600,000 examples.^[4] The M3A1 featured progressive refinements during its short wartime manufacturing phase, including a strengthened rear sight and a redesigned barrel collar that allowed the wire stock to double as a removal tool. Unloaded, the M3A1 weighed approximately 8 pounds, a slight reduction from the M3's 8.2 pounds due to simplified components like the removal of the oiler clip and lever assembly.^[2] Post-war production resumed during the Korean War, with Ithaca Gun Company manufacturing an additional 33,200 units to meet demand.^[2] Performance improvements in the M3A1 focused on reliability and maintainability, with the redesigned cocking slot and dust cover significantly reducing the incidence of malfunctions caused by dirt accumulation or component failure, as noted in field reports from late-war testing.^[17] The extended ejection port and integrated ejector groove on the bolt simplified disassembly, enabling quicker field stripping via a single takedown pin without specialized tools—operators could remove the barrel, bolt, and trigger group in seconds after clearing the weapon.^[16] These enhancements maintained the weapon's cyclic rate of around 450 rounds per minute while improving controllability through minor internal buffering adjustments that moderated bolt velocity.^[16] The M3A1 entered service alongside existing M3 stocks from late 1944, primarily equipping vehicle crews, paratroopers, and support personnel where compactness was essential, though limited wartime production meant few reached frontline units before the European Theater's conclusion.^[2] It became the standard .45-caliber submachine gun in U.S. inventories post-war, serving through the Korean and Vietnam conflicts until gradual replacement by rifles like the M16.^[4]

T29

The T29 was an experimental prototype developed in the fall of 1944 by the Guide Lamp Division of General Motors to adapt the M3A1 submachine gun for the .30 Carbine cartridge (7.62×33mm), aiming to provide U.S. forces with a higher-velocity weapon for extended engagement ranges inspired by the German Sturmgewehr 44 encountered in the field.^[7]^[10] This modification sought to leverage the .30 Carbine's superior ballistics over the standard .45 ACP, offering lighter recoil potential and better penetration while retaining the M3's compact, stamped-metal construction suitable for paratrooper and infantry use.^[7]^[10] Key design changes included lengthening the receiver and barrel to 14 inches to maximize muzzle velocity and reduce flash, enlarging the magazine well to accommodate 30-round M1 Carbine magazines (formed by linking two 15-round units), and modifying the operating mechanism to handle the higher chamber pressures.^[7]^[18] The blowback system was retained but updated with a heavier bolt, a spring-loaded ejector for reliable case expulsion, and a dual-spring arrangement—a shorter, stiffer recoil spring paired with a longer, lower-rate feed spring—to manage bolt cycling and ensure consistent operation.^[7] Three prototypes were fabricated, two with 14-inch barrels and one with an 8-inch barrel for comparative evaluation.^[18] Trials in late 1944 at the Springfield Armory involved firing approximately 1,500 rounds per prototype, demonstrating enhanced effective range—estimated up to 200 yards with the longer barrel—due to the .30 Carbine's velocity of around 1,900 feet per second, compared to the M3's .45 ACP at approximately 920 feet per second.^[7]^[19] However, the tests revealed significant drawbacks, including excessive muzzle flash and report from the higher-pressure cartridge, unreliable functioning such as failures to feed and eject, and increased mechanical complexity from the modified bolt and springs, which contributed to perceived excessive recoil in the compact frame.^[7]^[10] The T29 project was formally terminated on November 16, 1944, following the U.S. Army's adoption of the select-fire M2 Carbine in September 1944, which better addressed the demand for an intermediate-power personal defense weapon without requiring further refinement of the M3-based design.^[7]^[10] No production ensued, but the T29's emphasis on economical stamped components and caliber adaptability influenced postwar lightweight submachine gun concepts, though it saw no operational deployment.^[7]

9mm Conversion

The 9mm conversion of the M3 and M3A1 submachine gun involved field modifications to chamber the 9×19mm Parabellum cartridge, primarily to enable compatibility with allied and captured ammunition during World War II operations. These conversions were undertaken by the U.S. Ordnance Department, with Guide Lamp Division producing approximately 1,000 dedicated 9mm M3 models in 1943 for issuance to the Office of Strategic Services (OSS) and resistance groups in occupied Europe and the Pacific theater.^[2]^[20] The modification process required replacing the original .45 ACP barrel with a 9mm barrel assembly, installing a lighter 9mm-specific bolt, and fitting a magazine well adapter to accept 32-round British Sten magazines, while retaining the M3A1's improved features such as the dust cover ejection port. This setup allowed OSS operatives and allies like Norwegian and French resistance fighters to utilize locally available 9mm Parabellum rounds, reducing logistical burdens in areas where .45 ACP was scarce. An additional approximately 500 conversion kits—comprising the bolt (C153425), barrel assembly (C153435), and magazine adapter (C153430)—were produced by Rock Island Arsenal to enable on-site alterations of standard .45 models.^[21]^[5]^[22] Post-war, surplus M3/M3A1 guns underwent limited conversions by U.S. forces and allies to align with NATO standardization on 9mm ammunition, though these were not formally adopted as a variant but rather as practical field upgrades for reserve and training units. Commercial 9mm conversion kits became available starting in the 1980s through manufacturers like Indianapolis Ordnance and Buffalo Arms, allowing owners of semi-automatic replicas to adapt their weapons for 9mm use while preserving the original design's simplicity. The 9mm chambering provided noticeably reduced recoil compared to .45 ACP due to the lighter projectile and case, enhancing controllability during sustained fire, along with increased magazine capacity up to 40 rounds via extended Sten-compatible adapters in some kits. Muzzle velocity averaged around 1,200 feet per second from the 8-inch barrel, suitable for short-range engagements but with potential reliability challenges from inconsistent extraction of the thinner 9mm cases in the blowback mechanism optimized for .45 ACP.^[21]^[23]

Foreign Variants and Derivatives

Argentine PAM-1 and PAM-2

The Argentine PAM (Pistola Ametralladora Modelo) series consisted of licensed copies of the M3A1 submachine gun, produced domestically to equip the nation's military and police forces. Development began in the early 1950s under Fabricaciones Militares (FM), specifically at the Fábrica Militar de Armas Portátiles “Domingo Matheu” (FMAP-DM) in Rosario, as part of efforts to reduce reliance on imported weaponry. The PAM-1, introduced in 1954, was a near-direct adaptation of the M3A1's blowback-operated mechanism but chambered in 9×19mm Parabellum rather than .45 ACP, utilizing 30-round double-stack magazines compatible with the original design. Approximately 34,636 PAM-1 units were manufactured between 1954 and 1961, incorporating local steel components to support Argentina's industrial base.^[24]^[25] The PAM-2 variant emerged in the early 1960s to address safety concerns identified in the PAM-1, particularly accidental discharges from bolt inertia when dropped. Production of the PAM-2 involved converting about 16,544 existing PAM-1s between 1963 and 1972 by adding a grip safety lever at the rear of the magazine well, which required forward pressure to allow bolt movement. An additional 1,100 new PAM-2 units were built in 1969, maintaining the 9×19mm chambering, wire telescoping stock, and flip-up rear sight graduated for 50 and 100 meters. These modifications enhanced reliability without altering the core stamped-metal construction or cyclic rate of approximately 450 rounds per minute. Total PAM series production reached around 35,736 units by the early 1970s.^[24]^[26]^[27] During the Falklands War in 1982, PAM-2 submachine guns were issued to Argentine infantry and special forces, providing close-quarters firepower in trench and urban engagements, though many were captured by British troops. The series saw widespread adoption across Argentine Army, Navy, Air Force, and gendarmerie units until the mid-1970s, when it began to be supplanted by the domestically developed FMK-3 (also known as PAM-3). Despite the transition, PAM-1 and PAM-2 weapons remained in limited reserve and training roles into the 1990s, with surplus examples later demilitarized and sold as semi-automatic civilian firearms.^[25]^[28]^[26]

Chinese Type 36 and Type 37

The Chinese Type 36 submachine gun originated as a reverse-engineered copy of the American M3A1, developed by Nationalist forces during the Chinese Civil War in 1947 and chambered in .45 ACP.^[29] Produced at the Shenyang Arsenal (formerly the Mukden Arsenal) using captured U.S. Lend-Lease parts and local manufacturing techniques, it featured crude stamped metal construction that closely mirrored the M3A1 but with variations in finish quality and non-interchangeable components, such as the absence of barrel nut wrench flats and an oil reservoir in the pistol grip.^[29] Approximately 10,000 units were manufactured before Communist forces overran the facility in 1949, after which the weapons were captured and repurposed for People's Liberation Army (PLA) use.^[30] The Type 37, adopted in 1948, represented a refined 9mm Parabellum variant also derived from the M3A1, produced in limited numbers at the Jin Ling Arsenal in Nanking by the Nationalists.^[31] Key design modifications included an 8mm extension to the barrel and bolt recess to accommodate the smaller caliber, along with a spring steel adapter to utilize British Sten magazines, while retaining the blowback-operated mechanism and overall stamped sheet metal frame of the original.^[31] Production ceased abruptly in 1949 following the Communist capture of Nanking, with the Nationalists continuing a similar design on Taiwan as the Type 39; exact output figures for the mainland Type 37 remain unclear but were significantly lower than the Type 36 due to wartime disruptions.^[31] Both variants saw extensive service during the late stages of the Chinese Civil War (1945–1949), arming Nationalist troops before transitioning to PLA inventories through battlefield captures.^[29] The Type 36, in particular, was employed by the PLA during the Korean War (1950–1953), providing close-quarters firepower in infantry assaults despite its rudimentary build and reliance on captured .45 ACP ammunition.^[32] Some sub-variants were reportedly adapted for 7.62×25mm Tokarev rounds to align with Soviet-supplied logistics, enhancing compatibility with PPSh-41 stocks, though such conversions were not standardized.^[33] By the 1960s, both the Type 36 and Type 37 had become obsolete within the PLA, supplanted by more modern designs like the Type 56 assault rifle, but their stamped construction techniques influenced subsequent Chinese submachine gun developments, including the Type 79.^[31]

Other International Copies

In the 1950s, the Israeli Defense Forces acquired and employed U.S. surplus M3 submachine guns, often with local modifications to suit operational requirements, including adaptations for 9mm ammunition compatibility similar to contemporary U.S. conversion principles. These variants supported early IDF infantry and special units during formative conflicts, leveraging the M3's compact reliability in close-quarters scenarios. Norwegian military forces in the 1950s conducted upgrades on imported U.S. M3 surplus, converting them to 9mm chambering through locally machined components that mirrored American kits, including barrel replacements and magazine adapters, to align with NATO-standard ammunition. These efforts extended the weapon's service life in Norwegian hands amid post-war rearmament.

Operational History

World War II Use

The M3 submachine gun entered combat for the first time on June 6, 1944, during the Normandy invasion, where it was carried by paratroopers of the U.S. 82nd and 101st Airborne Divisions.^[2]^[4] Adopted in December 1942 and with production ramping up from May 1943, the weapon was initially issued in limited numbers to specialized units, including tank and armored vehicle crews, Office of Strategic Services (OSS) agents, and infantry support elements requiring a lightweight, compact firearm for close-quarters scenarios.^[2]^[34] In the European Theater, the M3 saw action in major engagements such as the D-Day landings and the Ardennes Offensive (Battle of the Bulge) in late 1944, where it equipped U.S. forces for defensive operations against German advances.^[2]^[35]^[36] Across the Pacific Theater, U.S. Marines employed the M3 in close-quarters fighting at Iwo Jima and Okinawa in 1945, valuing its maneuverability in confined spaces like caves and bunkers.^[2] Suppressed variants were particularly utilized by OSS agents for covert operations, where the weapon's reduced noise—described as a mild clap—supported intelligence gathering and harassment of Axis supply lines.^[2]^[37] Field reports on the M3's performance were mixed, with troops appreciating its reliability in adverse conditions such as mud, dust, and jungle humidity, which outperformed other submachine guns in environmental tests.^[2] However, early models drew criticism for a slow cyclic rate of about 450 rounds per minute—less than the Thompson's 700—and an awkward, flimsy cocking handle prone to bending or jamming under stress.^[34]^[37] Despite these issues, the design's stamped-metal construction proved durable for short-range engagements up to 50 yards, earning gradual acceptance among users.^[2] Logistically, the M3 addressed wartime shortages by supplanting the costly Thompson submachine gun ($225 per unit) in rear-echelon units and secondary roles, with its $20.94 production cost enabling mass issuance without extensive spare parts support—often treated as disposable until mid-1944.^[4]^[34] Its mechanical simplicity allowed for quick training of replacement troops, and by the end of hostilities in 1945, over 600,000 units had been produced and fielded, primarily by General Motors' Guide Lamp Division.^[5]^[4]

Post-War Conflicts

Following World War II, the M3 submachine gun and its M3A1 variant continued to see significant use in the Korean War (1950–1953), where it served as the primary submachine gun for U.S. and United Nations forces in close-quarters combat scenarios. Approximately 48,000 units were available in U.S. inventory by the conflict's outset, with an additional 33,000 M3A1s produced specifically for the war by Ithaca Gun Company. The weapon was particularly favored by vehicle crews and tankers for its compact size and reliability in confined spaces, such as during the intense fighting at the Chosin Reservoir, where Marines employed it against Chinese forces in subzero temperatures and rugged terrain.^[38]^[5]^[2] In the Vietnam War (1955–1975), the suppressed M3A1 variant proved especially valuable for special operations, with units like MACV-SOG (Military Assistance Command, Vietnam – Studies and Observations Group) and Navy SEALs using it for silent ambushes and reconnaissance missions deep in enemy territory. Its simple stamped-metal construction demonstrated exceptional durability in the humid, muddy jungle environment, where more complex weapons often jammed, allowing operators to maintain functionality under prolonged exposure to moisture and debris. The M3A1's .45 ACP round provided effective stopping power at short ranges typical of such operations, contributing to its preference over other submachine guns in these roles.^[39]^[2] Beyond these major conflicts, the M3 saw limited but notable employment in later engagements, including the 1991 Gulf War, where U.S. tank crews carried it as a personal defense weapon inside armored vehicles like the M1 Abrams for emergency dismounted actions. Argentine forces utilized the PAM variant—a 9mm derivative—in the 1982 Falklands War, though its role was marginal compared to rifles. The U.S. military phased the M3A1 out of frontline service in 1959 with the adoption of the M14 rifle but retained it in reserves for vehicle crews until 1992. Post-1991, no major conflicts featured the M3 prominently, though remnants appeared in occasional use by U.S. allies, such as Philippine Marines in training and low-intensity operations into the 2000s.^[38]^[25]^[40]

Users

National Military Operators

The United States was the primary operator of the M3 submachine gun, adopting it in 1943 as a low-cost replacement for the Thompson and issuing it to the Army, Marine Corps, and Air Force through 1992.^[4] It saw extensive service across World War II, the Korean War, the Vietnam War, and beyond, often as a defensive weapon for vehicle crews and special units, before being phased out in favor of the M16 rifle; limited numbers remained in storage for potential reactivation as of the late 1990s.^[38] South Korea received M3 submachine guns through U.S. military aid in the early 1950s during the Korean War, where they served as a standard issue alongside American forces until the conflict's end.^[5] The Philippines acquired surplus M3s post-World War II via U.S. assistance and maintained them in limited service for reserve and special operations units into the 2020s, particularly for maritime boarding teams, with local modifications including suppressors, red dot sights, and updated finishes to extend usability.^[41]^[42] South Vietnam utilized the M3 from the early 1960s until the fall of Saigon in 1975, supplied as part of U.S. aid to equip the Army of the Republic of Vietnam (ARVN) in close-quarters roles during the Vietnam War.^[38] Most national militaries retired the M3 by the early 2000s, replacing it with more versatile assault rifles, though variants persisted in secondary, ceremonial, or training capacities in select forces.^[43]

Non-State and Paramilitary Users

The M3 submachine gun saw employment by various non-state actors during and after World War II, often through supply, capture, or smuggling. In particular, the Office of Strategic Services (OSS) and Allied Jedburgh teams utilized the weapon for clandestine operations in occupied Europe, valuing its compact design and suppressed variants for sabotage and resistance support missions.^[44] During the Vietnam War, Viet Cong insurgents frequently captured M3s from South Vietnamese Army (ARVN) stocks and U.S. forces, adopting them as a reliable close-quarters weapon alongside their standard arms. These captures were common due to the M3's widespread issue to allied troops, allowing the Viet Cong to integrate the gun into guerrilla tactics without reliance on formal supply lines.^[38] In the context of the Northern Ireland Troubles, the Provisional Irish Republican Army (IRA) acquired M3 submachine guns through smuggling networks in the late 1960s and 1970s, employing them in urban ambushes, robberies, and assassinations throughout the 1970s and 1980s. The silenced versions proved especially suitable for the IRA's covert operations in populated areas.^[45] The Argentine PAM-1 and PAM-2 variants, direct derivatives of the M3, were used by local police and paramilitary security forces during internal conflicts, including operations against guerrilla groups in the 1970s and 1980s. These groups leveraged the PAM's simplicity and low cost for crowd control and counter-insurgency roles.^[25] Following the 1986 Hughes Amendment restricting new machine gun registrations in the United States, manufacturers produced semi-automatic replicas of the M3 for civilian collectors, sport shooters, and private security firms, maintaining the weapon's historical form while complying with federal laws. Examples include the Valkyrie Arms M3A1 pistol and carbine versions, which replicate the original's stamped-steel construction using surplus U.S. parts.^[46] By the 2010s, the M3's obsolescence limited its appeal to non-state actors. However, modern insurgents have largely favored more advanced small arms over the aging design.

References

[1]
[PDF] FM 23-41 SUBMACHINEGUNS - Wikimedia Commons
FM 23-41. DEPARTMENT OF THE ARMY FIELD MANUAL. SUBMACHINEGUNS. CALIBER .45 M3 AND M3A1. HEADQUARTERS, DEPARTMENT OF THE ARMY. 28 JUNE 1974. Page 2 ...
[2]
The Controversial M3 Grease Gun - Warfare History Network
The M3 submachine gun represented a triumph in low-cost mass production and was in service with the U.S. military for over 50 years.
[3]
[PDF] M3 & M3A1 SUBMACHINE GUNS J&M Spec. LLC
The M3 first saw service in mid-1944. The M3A1 was adopted in Dec. 44, and served from WWII through the. Gulf War, being officially retired in.
[4]
The M3 & M3A1 'Grease Guns' | An Official Journal Of The NRA
May 20, 2016 · A total of 606,694 M3 and 15,469 M3A1 submachine guns were manufactured during World War II. Several interesting accessories were developed for ...
[5]
U.S. General Motors Guide Lamp Division M3 Submachine Gun.
Adopted by the Army in December 1942 as the "Submachine Gun, Caliber .45, M3," these guns were manufactured by the Guide Lamp Division of General Motors.
[6]
The Modified M3 Grease Gun in WWII - World War Media
May 10, 2017 · 45 caliber submachine gun M3 is often indicated as being a success story of small arms design and development during World War II. Born of ...
[7]
WWII Grease Guns: How GM Helped GIs - Small Arms Review
Feb 12, 2019 · The M3 submachine gun design had begun as the T-15 prototype, which was developed by the Ordnance Department and the Inland Division of General Motors.<|control11|><|separator|>
[8]
M3 Grease Gun: Taking a Cheap Shot - The Armory Life
Jan 26, 2021 · Designed to be mass-produced at very low cost, the M3 Grease Gun went on to provide an incredible long-term return on investment.
[9]
WWII Allied Advantage: Unique M3 and M3A1 Grease Guns and ...
May 20, 2024 · Among the original specifications desired in the T-20 (M3) submachine gun was a kit to change the caliber to 9mm. The conversion kits were ...
[10]
World War II Field Fix for the M3 Grease Gun - American Rifleman
Feb 25, 2016 · The weapon's crank handle has been removed, a channel has been cut in the receiver and a makeshift cocking handle has been added to the bolt.Missing: telescoping failures
[11]
45 ACP Ballistics - Velocity, Energy, Drop & More - Ammo To Go
Jan 16, 2021 · Maximum pressure (SAAMI), 21,000 psi. 45 ACP ammo is still commonly equipped with a 230 grain bullet, although lighter bullets are available ...
[12]
Grease Gun M3-M3A1 - FM 23-41 - Internet Archive
Apr 14, 2014 · Grease Gun M3-M3A1 - FM 23-41 ; Topics: firing, bolt, trigger, cartridge, ammunition, submachinegun, magazine, sear, weapon, firer, guide rod, ...Missing: Army | Show results with:Army
[13]
Shooting the M3A1 Grease Gun - Forgotten Weapons
Mar 9, 2018 · The M3 “Grease Gun” (because really, that is what it looks like) was a very inexpensive weapon with a stamped and welded receiver and only a fed milled parts.
[14]
M3 .45 Caliber Submachine Gun - Gary's Place
May 10, 2006 · M3 .45 Caliber Submachine Gun. Gary's U.S. Infantry Weapons Reference Guide ; 8.0 in (203 mm) · R.H., four lands, pitch 1 in 16 inches (406 mm).
[15]
[PDF] FM 23-41 SUBMACHINEGUNS - EverySpec
The purpose of this manual is to pro- vide a source of information to individual soldiers and guide- lines to instructors on the Submachineguns, ...Missing: specifications | Show results with:specifications
[16]
At The Range: M3A1 Submachine Gun - American Rifleman
Nov 28, 2020 · When it went into production in May 1943 at General Motor's Guide Lamp Division plant in Anderson, Ind., the M3 was a reliable open-bolt ...
[17]
The Other .30 Carbine Firearms - The Mag Life - GunMag Warehouse
Sep 23, 2024 · 30-caliber rifle. The Army weapon development produced three prototypes. Two had 14-inch barrels, and one had an 8-inch barrel. T29 smg ...
[18]
The Springfield Armory National Historic Site (Part II)
Jan 17, 2019 · The T29 is a straight blowback M3A1 “Grease Gun” chambered for the .30 carbine cartridge. The barrel is 14 inches in length; the overall length ...
[19]
U.S. M3 Grease Gun - SWAT Survival | Weapons | Tactics
In addition to the 1,000 9mm M3s manufactured by Guide Lamp, another 500 or so conversion kits to switch an M3 from .45 ACP to 9mm were built by Rock Island ...
[20]
M3 Greasegun 9mm Conversion Kit - Small Arms Review
Jun 1, 2000 · The kit consists of a magazine adapter, 9mm barrel assembly, a special 9mm bolt and a standard 9mm British Sten magazine.
[21]
M3 Variants T20/M3A1 9MM/OSS M3/T20 - Suggestions - Enlisted
Jul 19, 2025 · In 1943, the Guide Lamp company produced about 1000 weapons chambered for 9x19mm Parabellum. The weapon had 9mm caliber barrels and a ...Missing: 600 | Show results with:600
[22]
Question about an M3 Grease Gun 9mm Conversion Kit
Mar 28, 2017 · I have finally acquire a 9mm conversion kit for my M3A1 Grease Gun. I made an oak box to store it in so all of the parts will remain together. ...<|control11|><|separator|>
[23]
Pistola Ametralladora P.A.M.: The Argentine Grease Gun
1972- conversion of 56 PAM 1 to PAM 2. Thus, the total production was at least 34,636 PAM 1, of which 16,544 weapons were subsequently converted to the model ...Missing: Fabricaciones | Show results with:Fabricaciones<|control11|><|separator|>
[24]
The Rosario “Grease Guns”: Argentina's P.A.M-1 and P.A.M.-2 SMGs
Jan 18, 2018 · The PAM-1 and PAM-2 submachine guns that once armed Argentine military and police forces are part of the extended family of the legendary General Motors Grease ...
[25]
PAM-2: Argentina's Improved 9mm Grease Gun - Forgotten Weapons
Jun 24, 2024 · The Argentine factory FMAP-DGFM was first set up to produce a copy of the Colt 1911, and in 1954 they began production of the PAM-1 (after ...
[26]
P.A.M.1 and P.A.M.2: Argentina's "Grease Guns" - The Firearm Blog
Apr 25, 2017 · The Argentine “Grease Guns” remained in service with the local Army, Navy, Air Force and Police agencies for quite some time.
[27]
FMK-3 Submachine Gun — Argentina's Uzi? - The Armory Life
Jul 9, 2024 · The Argentine FMK-3 was developed to replace their M3 Grease Gun clone, called the P.A.M 1. The blowback-operated SMG first saw use in ...
[28]
THE CHINESE TYPE-36 "GREASE GUN" - Small Arms Review
Dec 1, 2012 · 45 caliber, Type-36. The designation came from the Chinese Republic calendar year that started in 1911 when the Republic of China was ...
[29]
Type 36 submachine-gun | Imperial War Museums
Chinese Nationalist copy of M3A1. Approx 10,000 of the Type 36 were produced before Mukden fell to Communists. Chinese inscription over stamped on left of ...
[30]
THE CHINESE TYPE 37 GREASE GUN - Small Arms Review
Nov 4, 2010 · The first Chinese M3A1 clone produced on mainland China was adopted in 1947 and thus designated as the Type 36. The designation came from the ...
[31]
Communist Small Arms Of The Korean War - American Rifleman
Feb 6, 2021 · Throughout the Korean War, Communist North Korean and Chinese forces used a variety of small arms from different sources to arm their ...
[32]
The Type 36 and 37 - The Chinese Grease Guns and Their Impact
The Type 36 an later 37 submachine guns were designed by the Chinese and manfuactured in small batches and effectively used in WW2 and beyond.
[33]
Madsen M1945 submachine gun - Modern Firearms
Madsen M1945 submachine gun was developed in 1945 by famous Danish arms-making company Dansk Industrie Syndikat AS (DISA), better known for its trade mark “ ...
[34]
Valkyrie Arms Semiauto M3A1 Grease Gun - Forgotten Weapons
Dec 3, 2019 · Ian mentioned that some customer service issues occurred with the Valkyrie Arms M3 Grease Gun replica. I personally know of one sad story. A ...
[35]
How the M3 "Grease Gun" Gained a Foothold in Combat - ITS Tactical
Aug 28, 2017 · Made of stamped metal parts like a General Motors car, the M3 is not a submachine gun noted for its fine tolerances and sleek design. It's ...
[36]
Battle of the Bulge: The Guns of America & Germany
Dec 16, 2022 · It was, in fact, the only submachine in production when the war started but was joined later by the M3 “Grease Gun.” German Soldiers M1928 A ...Battle of the Bulge: Rifles... · Battle of the Bulge: Pistols · Battle of the Bulge...
[37]
The Battle of the Bulge at 75: The Guns They Carried
Dec 15, 2019 · However, they were already headed out of production in favor of the smaller, and much cheaper, M3 Grease Gun, especially with Patton's tank ...
[38]
This Classic Submachine Gun Fought With The Resistance In ...
Feb 1, 2017 · Though happy with the basic product, the Army was interested in adding a suppressor to the Grease Gun. Reducing the noise and flash at the ...
[39]
M3 Grease Gun in the Cold War & Beyond - The Armory Life
Jul 6, 2021 · The fragile crank-like cocking lever was discarded and replaced by a cocking slot that was machined into the bolt itself. ... M3 submachine gun ...A Solid Foundation · The Korean War · The Tankers' Gun<|control11|><|separator|>
[40]
The gear that MACV-SOG warriors carried and how it's still relevant ...
Dec 19, 2022 · Others would carry a variety of weapons, such as AK-47s, cutdown Russian-made RPD light machine guns, silenced M3 .45 caliber submachine guns ( ...
[41]
Following M3A1 Grease Gun #750213 Through Vietnam | RECOIL
Feb 22, 2021 · The Army touted it as more accurate than the Thompson, claiming a soldier firing an M3 full-auto offhand would keep 90 percent of his rounds ...
[42]
The Philippine Militarys Suppressed Grease Guns - The Firearm Blog
Mar 1, 2016 · The Philippine Marines currently still use the M3 for boarding ships. Their armorers outfitted their old M3s with a red dot, a suppressor and a new paint job.Missing: submachine | Show results with:submachine
[43]
The Philippine Marines Teach an Old Submachine Gun New Tricks
Apr 25, 2016 · The M3 SpecOps Generation 2 , also known as the M3 Gen2 or PN/PMC M3, is a modified, modern incarnation of the M3 grease gun built from pre- ...
[44]
Submachine Gun, Cal. .45, M3/M3A1 - GlobalSecurity.org
Jul 7, 2011 · Submachine guns are still used by Special Forces, air crews, armored vehicles, counter-terrorist units, and Naval personnel (679,200). M3 (1942 ...
[45]
Weapons of the OSS Jedburgh Teams - Gunpowder Magazine
Jan 4, 2022 · These included large quantities of M1 or M1A1 Thompson submachine guns in .45 ACP, M3 “Grease Gun” submachine guns in both .45 ACP and 9mm ...
[46]
Silent but Deadly: The Suppressed M3 M3A1 - Small Arms Review
Dec 1, 2016 · These deliveries included M1 Carbines as well as M3 Grease Guns, which were used by the IRA in attacks and robberies. Some of the M3s captured ...<|separator|>
[47]
Philippines pt.2: WWII weapons used 1946-2018 - wwiiafterwwii
Nov 18, 2018 · In the Philippines military, the M3 was greatly liked due to it's light weight, ease of maintenance, and ammunition commonality with the M1911.