The M3 is an American .45-caliber submachine gun adopted by the U.S. Army on 12 December 1942, as the United States Submachine Gun, Cal. .45, M3.Iannamico, Frank, The U.S. M3-3A1 Submachine Gun, Moose Lake Publishing, , (1999), pp. 14, 22–24, 34–39, 44–46, 54–55, 59–63, 67, 73–74 The M3 was chambered for the same .45 ACP round fired by the Thompson submachine gun, but was cheaper to mass produce and lighter, at the expense of accuracy. The M3 was commonly referred to as the "Grease Gun" or simply "the Greaser", owing to its visual similarity to a grease gun, a mechanic's tool.Ingram, Mike: The MP40 Submachine Gun, p. 85. Zenith Imprint, 2001.
The M3 was intended as a replacement for the Thompson submachine gun, and began to enter frontline service by mid-1944. By late 1944, the M3A1 variant was introduced, which also saw use in the Korean War and later conflicts.
The M14 rifle, adopted in 1959, was intended to replace the M3A1 (as well as the M1 Garand, M1918 Browning Automatic Rifle and the M1 carbine)Thompson, Leroy (2014). The M14 Battle Rifle. Weapon 37. Osprey Publishing. , p. 12 but the recoil of the M14's 7.62×51mm NATO cartridge proved too powerful for the submachine gun role. The M14 was in turn replaced by the M16 rifle in 1964, and this weapon and its subsequent shorter iterations (XM-177, firing the intermediate 5.56×45mm NATO cartridge) was a better replacement for the M3A1. M3A1 submachine guns were retired from U.S. frontline service after 1959, but continued to be issued, for example as backup weapons for armored vehicle crews as late as the Gulf War (1990–1991). Many overseas US military bases continued to issue these for certain crews into the mid to late 1990s.
History
In 1941, the U.S. Army Ordnance Board observed the effectiveness of submachine guns employed in Western Europe, particularly the German 9×19mm MP 40 and British Sten submachine gun and initiated a study to develop its own "Sten" type submachine gun in October 1942. The Ordnance Department requested the Army submit a list of requirements for the new weapon, and Ordnance in turn received a separate list of requirements from both the Infantry and Cavalry branches for a shoulder-fired weapon with full or semiautomatic fire capability in caliber .45 ACP or .30 Carbine.
The two lists of requirements received by Ordnance were then reviewed and amended by officials at Aberdeen Proving Ground (APG). The amended requirement called for a weapon of all-sheet metal construction in .45 ACP, designed for fast and inexpensive production with a minimum of machining and featuring both fully automatic and semi-automatic fire capabilities, a heavy bolt to keep the cyclic rate of fire under 500 rounds per minute and the ability to place 90% of shots fired from a standing position in full automatic mode on a 6x6 feet target at a range of 50 yards. The benchmark for testing the M3's performance would be the M1928A1 Thompson.
George Hyde of General Motors' Inland Division was given the task of designing the new weapon, while Frederick Sampson, Inland Division's chief engineer, was responsible for preparing and organizing tooling for production. The original T15 specifications of 8 October 1942 were altered to remove the semi-automatic fire function, as well as to permit installation of a kit to convert the weapon's original .45 caliber to that of 9 mm Parabellum. The new designation for the 9 mm/.45 full-automatic-only weapon was the T20.
Five prototype models of the .45 T20 and five 9 mm conversion kits were built by General Motors for testing. At the initial military trials, the T20 successfully completed its accuracy trials with a score of 97 out of 100. In the endurance test, the test weapon fired more than 5,000 rounds of brass-case ammunition, with only two failures to feed. Four army test boards composed of multiple army service branches independently tested and reviewed the T20 prototype weapons including the Airborne Command, the Amphibious Warfare Board, the Infantry Board, and the Armored Force Board. All four branches reported malfunctions caused by the magazine, mostly attributed to defective or jammed magazine followers.
The T20 was formally approved by U.S. Army Ordnance for production at GM's Guide Lamp Division in Anderson, Indiana, in December 1942 as the U.S. Submachine Gun, Caliber .45, M3. Guide Lamp produced 606,694 of the M3 variant submachine gun between 1943 and 1945. Although reports of malfunctions caused by the single-feed magazine design appeared during the initial firing trials, no changes were made to the M3 magazine.
Around 1,000 M3 submachine guns in caliber 9 mm Parabellum were built by Guide Lamp.Cadiou, Yves, and Richard, Alphonse, Modern Firearms, Secaucus, New Jersey: Chartwell Books, (1977), p. 210 These original 9 mm guns, identified by the markings U.S. 9 mm S.M.G. on the left side of the magazine well (without any model designation, such as M3), were delivered to the OSS in 1944. The 9mm M3 was also supplied to the French, Belgian, Dutch, Italian and Norwegian resistance groups so that captured German ammo could be used thus reducing the need for .45 ACP ammo resupply drops from the OSS and the SOE. Additionally, Rock Island Arsenal and Buffalo Arms Corporation manufactured parts for a limited number of 9 mm conversion kits for the M3.Iannamico, pp. 122–123 Though 25,000 kits were originally requested for procurement, this was changed to a recommendation by the Ordnance Committee in December 1943 that only 500 9 mm conversion kits be obtained. Procurement was authorized in February 1944, but it is believed that only a limited number of kits were actually produced. These conversion kits included a new 9 mm barrel, replacement bolt and recoil springs, a magazine well adapter for use with British Sten gun 32-round magazines, and a replacement 9 mm Sten magazine of British manufacture. As the M3's sights were not altered for the new cartridge, the 9 mm M3 shot high at 100 yards, but the sighting error was deemed inconsequential. The OSS also requested approximately 1,000 .45-caliber M3 submachine guns with an integral sound suppressor designed by Bell Laboratories. Specially- drilled barrels and barrel nuts were manufactured by Guide Lamp, while the High Standard Firearms Company produced the internal components and assembled the weapon.Iannamico, pp. 106–107 The Bell Laboratories suppressor was estimated to be only 80% as efficient as the British suppressed STEN Mk IIS.Iannamico, p. 108
With its stamped, riveted, and welded construction, the M3 was originally designed as a minimum-cost small arm, to be used and then discarded once it became inoperative.Dunlap, Roy, Ordnance Went Up Front, Samworth Press (1948), p. 3002nd Ranger Battalion, World War II Living History Group, M3A1 Submachine Gun As such, replacement parts, weapon-specific tools, and sub-assemblies were not made available to unit-, depot-, or ordnance-level commands at the time of the M3's introduction to service.Dunlap. p. 3002nd Ranger Battalion, M3A1 Submachine Gun In 1944, a shortage of M3 submachine guns created by the need for interim production changes forced U.S. Army Ordnance workshops to fabricate pawl springs and other parts to keep existing weapons operational.2nd Ranger Battalion, World War II Living History Group, M3A1 Submachine Gun. Retrieved on September 19, 2008.
After its introduction to service, reports of unserviceability of the M3 commenced in February 1944 with stateside units in training, who reported early failure of the cocking handle/bolt retraction mechanism on some weapons. Similar reports later came from U.S. forces in Britain who were issued the M3. An investigation revealed several deficiencies in the construction of the M3's bolt retraction mechanism, together with issues concerning barrel removal and retention as well as easily bent rear sights. As a result, several product improvements were incorporated into all new M3 production, including a new design retracting pawl with improved heat treatment, a new spring stop fitted to the right-hand brace of the retracting lever, a modified ejector featuring a cocking lever trip, a larger ratchet pad with improved heat treatment to more securely retain the barrel assembly, and strengthening gussets fitted to the sides of the fixed 'L' rear sight. After new complaints were raised about accidental magazine releases and failure of the wire buttstock to remain in place in the collapsed position, two additional changes were made to M3 production and approved by Ordnance on 31 August 1944. This included a small sheet metal guard around the magazine release button, and the inclusion of a stop between the two rods forming the wire stock at the butt end.
The M3 submachine gun was suitable for issue to tank crews, drivers, and paratroopers because of its compact design. The M3 was also ideal for the Pacific War because the Thompson could easily jam if not cleaned, which had to be done constantly in the jungle environment because the action did not have a cover over the ejector as the M3 did.
The improved and simplified M3A1 variant was introduced in December 1944 in response to field requests for further improvements to the basic M3 design; 15,469 were produced before the end of World War II, and an additional 33,200 during the Korean War.
It was originally hoped that the M3 could be produced in numbers sufficient to cancel future orders for the Thompson submachine gun, and to allow the Army to gradually withdraw the more expensive Thompson from front-line service. However, due to unforeseen production delays and requests for modifications, the M3 was introduced later than expected, and purchases of the Thompson continued until February 1944. The M3 first entered combat service in the summer of 1944. A total of 622,163 M3/M3A1 submachine guns of all types were assembled by the end of World War II.
The M3 became the main submachine gun over the Thompson for the U.S. and South Korean forces during the Korean War, because the Communists used the Thompson submachine gun, which the U.S. donated during World War II, as one of their main weapons during the war.
The M3 and M3A1 were largely withdrawn from U.S. frontline service beginning in 1959. But it continued to be issued until at least the 1991 Gulf War as equipment aboard armored vehicles, in particular the M60 tank (which was used by some United States National Guard units until 1997).Thompson, Leroy (19 May 2016). The M3 "Grease Gun". Weapon 46. Osprey Publishing. ISBN 978-1-4728-1107-3, p. 62
In the Vietnam War, suppressed versions were made with removable barrels that can be installed after taking a standard barrel out, the former made by Guide Lamp.
It was also the initial submachine gun equipping the Delta Force (formed in 1977) who prized it for its impressively quiet performance when equipped with a suppressor.Eric Haney, Inside Delta Force; The Story of America's Elite Anti-terrorist Unit, p. 130 Within a year, the M3A1 had been replaced by the 9 mm Heckler & Koch MP5 submachine gun in Delta Force use, but a few were kept past that date as it was felt that the M3A1 performed better with a suppressor than the MP5. Delta Force M3A1s were fitted with thumb safeties.Thompson, Leroy (19 May 2016). The M3 "Grease Gun". Weapon 46. Osprey Publishing. , p. 64
During the Troubles, some of the M3A1s captured from the Provisional Irish Republican Army by British forces were equipped with suppressors.
Design details