Thompson submachine gun
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|Thompson Submachine Gun, Caliber .45|
M1928A1 Thompson wartime production variant
|Place of origin||United States|
1938–1971 (officially, U.S. military)1938–present (other countries)
|Used by||See Users|
|Designer||John T. Thompson|
|Number built||Approx. 2,000,000|
|Variants||See Variants section|
|Cartridge||.45 ACP (11.43×23mm)|
|Action||Blowback, Blish Lock|
|Rate of fire||600–725 rpm (M1928), 700 rpm (M1A1), 1500 rpm (M1919)|
|Muzzle velocity||935 ft/s (285 m/s)|
|Effective firing range||150m|
The Thompson submachine gun is an American submachine gun, invented by John T. Thompson in 1918, that became infamous during the Prohibition era. It was a common sight in the media of the time, being used by both law enforcement officers and criminals. The Thompson submachine gun was also known informally as the "Tommy Gun", "Annihilator", "Chicago Typewriter", "Chicago Piano", "Chicago Style", "Chicago Organ Grinder", "Trench Broom", "Trench Sweeper", "The Chopper", and simply "The Thompson".
The Thompson was favored by soldiers, criminals, police, and civilians alike for its large .45 ACP cartridge, accuracy, and high volume of automatic fire. It has since gained popularity among civilian collectors for its historical significance. It has had, and continues to have, considerable significance in popular culture, especially in works about the U.S.'s Prohibition era and World War II, and hence is among the best-known firearms in recent history. Although the original fully automatic Thompsons are no longer produced, numerous semi-automatic civilian versions are still being manufactured by Auto Ordnance. These retain a similar appearance to the original models, but they have various modifications in order to comply with US firearm laws.
- 1 History and service
- 2 Collector interest
- 3 Features
- 4 Variants
- 4.1 Prototypes
- 4.2 Production
- 4.3 Service variants
- 4.4 Semi-automatic
- 4.5 Export variants
- 4.6 RPB Thompsons
- 5 Civilian ownership
- 6 Users
- 7 See also
- 8 References
- 9 External links
History and service
The Thompson Submachine Gun was developed by General John T. Thompson who originally envisioned an "auto rifle" (semi-automatic rifle) to replace the bolt action service rifles then in use. While searching for a way to allow such a weapon to operate safely without the complexity of a recoil or gas operated mechanism, Thompson came across a patent issued to John Bell Blish in 1915 based on adhesion of inclined metal surfaces under pressure. Thompson found a financial backer, Thomas F. Ryan, and started the Auto-Ordnance Company in 1916 for the purpose of developing his "auto rifle". It was primarily developed in Cleveland, Ohio. The principal designers were Theodore H. Eickhoff, Oscar V. Payne, and George E. Goll. By late 1917, the limits of the Blish Principle were discovered: rather than working as a locked breech, it functioned as a friction-delayed blowback action. It was found that the only cartridge currently in U.S. service suitable for use with the lock was the .45 ACP round. Thompson then envisioned a "one-man, hand-held machine gun" in .45 ACP as a "trench broom" for use in the ongoing trench warfare of World War I. Payne designed the gun itself and its stick and drum magazines. The project was then titled "Annihilator I" and by 1918, most of the design issues had been resolved. However, the war ended two days before prototypes could be shipped to Europe.
At an Auto-Ordnance board meeting in 1919 to discuss the marketing of the "Annihilator", with the war now over, the weapon was officially renamed the "Thompson Submachine Gun". While other weapons had been developed shortly prior with similar objectives in mind, the Thompson was the first weapon to be labeled and marketed as a "submachine gun". Thompson intended the weapon as an automatic "trench-broom" to sweep enemy troops from the trenches, filling a role for which the Browning Automatic Rifle (BAR) had been proven ill-suited. This concept had already been developed by German troops using their own Bergmann MP 18, the world's first submachine gun, in concert with Sturmtruppen tactics.
The Thompson first entered production as the M1921. It was available to civilians, although poor sales resulted from the expense of the weapon: the Thompson gun, with one Type XX 20 shot "stick" magazine, was priced at $200.00 in 1921 (equivalent to $2,653 in 2018). M1921 Thompsons were sold in small quantities to the United States Postal Inspection Service (to protect the mail from a spate of robberies) and to the United States Marine Corps. Federal sales were followed by sales to several police departments in the US and minor international sales to various armies and constabulary forces, chiefly in Central and South America. The Marines used their Thompsons in the Banana Wars and in China. It was popular with the Marines as a point-defense weapon for countering ambush by Nicaraguan guerrillas, and led to the organization of four-man fire teams with as much firepower as a nine-man rifle squad. The major complaints against the Thompson were its weight, inaccuracy at ranges over 50 yards (46 m), and the lack of penetrating power of the .45 ACP pistol cartridge.
Some of the first batches of Thompsons were bought in America by agents of the Irish Republic, notably Harry Boland. The first test of a Thompson in Ireland was performed by West Cork Brigade commander Tom Barry in presence of IRA leader Michael Collins. A total of 653 were purchased, but 495 were seized by US customs authorities in New York in June 1921. The remainder made their way to the Irish Republican Army by way of Liverpool and were used in the last month of the Irish War of Independence (1919–21). After a truce with the British in July 1921, the IRA imported more Thompsons and they were used in the subsequent Irish Civil War (1922–23). They were not found to be very effective in Ireland; in only 32% of actions where it was used did the Thompson cause serious casualties (death or serious injury) to those attacked.
The Thompson achieved most of its early notoriety in the hands of Prohibition and Depression-era gangsters, motorized bandits and the lawmen who pursued them, and in Hollywood films about their exploits, most notably in the St Valentine's Day Massacre. The two Thompson guns used in the massacre, called "the most famous murder weapons in the world", are still held by the Berrien County Sheriff's Department. It has been referred to by one researcher as the "gun that made the twenties roar".
In 1926, the Cutts Compensator (a recoil brake) was offered as an option for the M1921; Thompsons with the compensator were cataloged as No. 21AC at the original price of $200.00, with the plain M1921 designated No. 21A at a reduced price of $175.00.
In 1928, Federal Laboratories took over the distribution of the weapon from Thompson's Auto Ordnance Corporation. The cost at this time was $225 per weapon (equivalent to $3,101 in 2018), with $5 per 50-round drum and $3 for 20-round magazine.
Nationalist China acquired a quantity for use against Japanese land forces, and eventually began producing copies of the Thompson in small quantities for use by its armies and militias. In the 1930s, Taiyuan Arsenal produced copies of the Thompson for Yan Xishan, the warlord of Shanxi province.
World War II
In 1938, the Thompson submachine gun was adopted by the U.S. military, serving during World War II and beyond.
There were two military types of Thompson SMG.
- The M1928A1 had provisions for box and drum magazines. It had a Cutts compensator, cooling fins on the barrel, employed a delayed blowback action and its charging handle was on the top of the receiver.
- The M1 and M1A1 had a barrel without cooling fins, a simplified rear sight, provisions only for box magazines, employed a straight blowback action and the charging handle was on the side of the receiver.
Over 1.5 million military Thompson submachine guns were produced during World War II.
Military users of the M1928A1 had complaints about the "L" fifty-round drum magazine; the British Army officially criticised "their excessive weight, the rattling sound they made" and shipped thousands back to the U.S. in exchange for box magazines. The Thompson had to be cocked, bolt retracted ready to fire, to attach the drum. It attached and detached by sliding sideways, which made magazine changes slow and also created difficulty in clearing a cartridge malfunction ("jam"). Reloading an empty drum with cartridges was an involved process.
In contrast, the "XX" twenty-round box magazine was light and compact, it tended not to rattle, and could be inserted with the bolt safely closed. It was quickly attached and detached and was removed downward, making clearing jams easier. The box tripped the bolt open lock when empty, facilitating magazine changes. An empty box was easily reloaded with loose rounds. However, users complained it was limited in capacity. In the field, some soldiers taped two "XX" magazines together in what would be known as "jungle style" to speed magazine changes.
Two alternatives to the "L" drum and "XX" box magazines were tested December 6, 1941, at Fort Knox: an extended thirty-round box magazine and a forty-round magazine made by welding two 20-round magazines face to face, jungle style. Testers considered both superior to either the "XX" box or "L" drum. The 30-round box was approved as standard in December 1941 to replace the "XX" and "L" magazines. (The concept of welding two box magazines face-to-face was carried over with the UD 42 submachine gun.)
The staff of Savage Arms looked for ways to simplify the M1928A1, producing a prototype in February 1942 which was tested at Aberdeen Proving Ground in March 1942; Army Ordnance approved adoption as the M1 in April 1942. M1s were made by Savage Arms and by Auto-Ordnance. M1s were issued with the 30-round box magazine and would accept the earlier 20-round box, but would not accept the drum magazine.
The Thompson was used in World War II in the hands of Allied troops as a weapon for scouts, non-commissioned officers (corporal, sergeant, and higher), and patrol leaders, as well as commissioned officers, tank crewmen, and soldiers performing raids on German positions. In the European theater, the gun was widely utilized in British and Canadian commando units, as well as in the U.S. Army paratrooper and Ranger battalions, where it was issued more frequently than in line infantry units because of its high rate of fire and its stopping power, which made it very effective in the kinds of close combat these special operations troops were expected to undertake. Military Police were fond of it, as were paratroopers, who "borrowed" Thompsons from members of mortar squads for use on patrols behind enemy lines.[page needed] The gun was prized by those lucky enough to get one and proved itself in the close street fighting that was encountered frequently during the invasion of France. A Swedish variant of the M1928A1, the Kulsprutepistol m/40 (submachine gun, model 40), served in the Swedish Army between 1940 and 1951. Through Lend-Lease, the Soviet Union also received the Thompson, but due to a shortage of appropriate ammunition, its use was not widespread.
In the Malayan Campaign, the Burma Campaign and the Pacific Theater, Lend-Lease issue Thompsons were used by the British Army, Indian Army, Australian Army infantry and other Commonwealth forces. They used the Thompson extensively in jungle patrols and ambushes, where it was prized for its firepower, though it was criticized for its hefty weight and poor reliability. Difficulties in supply eventually led to its replacement in Australian Army units in 1943 by other submachine guns such as the Owen and Austen. The Thompsons were then given to the Royal Australian Air Force and Royal Australian Navy. New Zealand commando forces initially used Thompsons but switched them for the more reliable, lighter, and more accurate Owen during the Solomon Islands and Guadalcanal campaigns. The U.S. Marines also used the Thompson as a limited-issue weapon, especially during their later island assaults. The Thompson was soon found to have limited effect in heavy jungle cover, where the low-velocity .45 bullet would not penetrate most small-diameter trees or protective armor vests. (In 1923, the Army had rejected the .45 Remington–Thompson, which had twice the energy of the .45 ACP). In the U.S. Army, many Pacific War jungle patrols were originally equipped with Thompsons in the early phases of the New Guinea and Guadalcanal campaigns, but soon began employing the BAR in its place as a point defense weapon.
The Army introduced the U.S. M3 and M3A1 submachine guns in 1943 with plans to produce the latter in numbers sufficient to cancel future orders for the Thompson, while gradually withdrawing it from the first-line service. However, due to unforeseen production delays and requests for modifications, the M3/M3A1 never replaced the Thompson, and purchases continued until February 1944. At the end of World War II, the Thompson, with a total wartime production of over 1.5 million, outnumbered the M3/M3A1 submachine guns in service by nearly three to one.
After World War II
Thompson submachine guns were used by both sides during the 1948 Arab-Israeli war. Following the war, Thompsons were issued to members of Israel’s elite Unit 101, upon the formation of that unit in 1953.
During the Greek Civil War, the Thompson submachine gun was used by both sides. The Hellenic Armed Forces, gendarmerie and police units were equipped with Thompson submachine guns supplied by the British and later in the war by the United States. The opposing Communist fighters of the Democratic Army of Greece were also using Thompson submachine guns, either captured from government forces or inherited from ELAS. ELAS was the strongest of the resistance forces during the period of Greek Resistance against the Germans and Italians and were supplied with arms from both the British and the United States. After the demobilization of ELAS, an unspecified number of arms were not surrendered to the government but kept hidden, and were later used by the Democratic Army of Greece.
By the time of the Korean War, the Thompson had seen much use by the U.S. and South Korean military, even though Thompson had been replaced as standard issue by the M3/M3A1. With huge numbers of guns available in army ordnance arsenals, the Thompson remained classed as Limited Standard or Substitute Standard long after the standardization of the M3/M3A1. Many Thompsons were distributed to Chinese armed forces as a military aid before the fall of Chiang Kai-shek's government to Mao Zedong's Communist forces in 1949 during the Chinese Civil War. During the Korean War, American troops were surprised to encounter Chinese Communist troops heavily armed with Thompsons, especially during surprise night assaults. The gun's ability to deliver large quantities of short-range automatic assault fire proved very useful in both defense and assault during the early part of the conflict. Many of these weapons were captured and placed into service with American soldiers and Marines for the balance of the war.
During the Cuban Revolution, the Thompson submachine gun was used by some of Fidel Castro's guerrillas.
During the Vietnam War, some South Vietnamese army units and defense militia were armed with Thompson submachine guns, and a few of these weapons were used by reconnaissance units, advisors, and other American troops. It was later replaced by the M16 assault rifle. Not only did some U.S. soldiers have use of them in Vietnam, but they encountered them as well. The Viet Cong liked the weapon and used both captured models as well as manufacturing their own copies in small jungle workshops.
The Australian government destroyed most of their Thompson machine carbines in the 1960s. They shipped their remaining stocks to arm the forces of Lon Nol's Khmer Republic in 1975. They were then captured and used by the Khmer Rouge.
In the conflict in Northern Ireland, known as the Troubles (1969–1998), the Thompson was again used by the Irish Republican paramilitaries. According to historian Peter Hart, "The Thompson remained a key part of both the Official IRA and Provisional IRA arsenals until well into the 1970s when it was superseded by the Armalite and the AK-47."
The Thompson was also used by U.S. and overseas law enforcement and police forces, most prominently by the FBI. The FBI used Thompsons until they were declared obsolete and ordered destroyed in the early 1970s.
Because of their quality and craftsmanship, as well as their gangster-era and WWII connections, Thompsons are sought as collector's items. There were fewer than 40 pre-production prototypes. The Colt Patent Fire Arms Manufacturing Company in Hartford, Connecticut was contracted by the Auto-Ordnance Corporation to manufacture the initial mass production of 15,000 Thompson Submachine Guns in 1920. An original Colt Model 1921 A or AC, Model 1927 A or AC, Model 1928 Navy A or AC, properly registered in working condition with original components can easily fetch from US$25,000 to $45,000+ depending on condition and accessories. For WWII, approximately 1,700,000 Thompson Submachine Guns were produced by Auto-Ordnance and Savage Arms, with 1,387,134 being the simplified World War II M1 and M1A1 variants (without the Blish lock and oiling system).
A Model 1921A believed to have been owned by Bonnie and Clyde, but without historical documentation to substantiate this provenance, sold at auction on January 21, 2012, in Kansas City for $130,000.
Early versions of the Thompson, the Model of 1919, had a fairly high cyclic rate of fire, as high as 1,200 rounds per minute (rpm), with most Model of 1921 at 800 rpm. In 1927, the U.S. Navy ordered 500 Thompsons but requested a lower rate of fire. Thompson requested Payne develop a method of reducing the cyclic rate of fire. Payne replaced the actuator with a heavier one and the recoil spring with a stiffer one; the changes reduced the rate of fire from 800 to the 600 rpm of the U.S. Navy Model of 1928. Later M1 and M1A1 Thompsons averaged also 600 rpm. This rate of fire, combined with a rather heavy trigger pull and a stock with an excessive drop, increases the tendency for the barrel to climb off target in automatic fire. Compared to modern 9mm submachine guns, the .45 Thompson is quite heavy, weighing roughly the same as the contemporary M1 Garand semi-automatic rifle, and requires lots of cleaning. This was one of the major complaints against the weapon made by service members of the U.S. Army issued the Thompson.
Although the drum magazine provided significant firepower, in military service it was found to be overly heavy and bulky, especially when slung on patrol or on the march. The M1 Thompson drum magazine was rather fragile, and cartridges tended to rattle inside it, producing unwanted noise. For these reasons, the 20-round and later 30-round box magazines soon proved most popular with military users of the M1928A1, and drum compatibility was not included in the design of the wartime M1 and M1A1 models. The Thompson was one of the earliest submachine guns to incorporate a double-column, double-feed box magazine design, which undoubtedly contributed to the gun's reputation for reliability. In addition, the gun performed better than most after exposure to rain, dirt, and mud.
The selective-fire (semi- or fully automatic) Thompson fires from the "open bolt" position, in which the bolt is held fully to rearward by the sear when cocked. When the trigger is depressed, the bolt is released, traveling forward to chamber and simultaneously fire the first and subsequent rounds until either the trigger is released or the ammunition is exhausted. This eliminates the risk of "cook-off", which can sometimes occur in closed-bolt automatic weapons.
The Thompson submachine gun varies in field strip procedure, depending on the variant. World War II-era M1 variants and RPB models field strip more easily than the M1921.
The 1928 variant can be disassembled easily by first detaching the stock, then sliding off the lower receiver and then simply removing the internal parts, cleaning them, and then putting it back together. When opened up, the Thompson features a shockingly small amount of parts that need to be removed including the spring, bolt, Blish Lock, and actuator bolt.
Persuader and Annihilator
There were two main experimental models of the Thompson. The Persuader was a belt-fed version developed in 1917/18. It was partially built, but never completely finished. The Annihilator, serial no. 1 to 10, was similar in appearance to the later models, but without rear sight and butt stock mounts. The first were fed from a 20-round box magazine, later, the 50- and 100-round drum magazines were developed.
Starting with the Serial no. 11, the Model of 1919 takes the final appearance of the later Thompsons with the rear sights and the butt stock. The Model 1919 was limited to about 40 units; the first built did not use the drums, as it was too difficult to fire. Many variations have been noted within this model. The weapons had very high cyclic rates up to 1,500 rpm. This was the weapon Brigadier General Thompson demonstrated at Camp Perry in 1920. A number of Model of 1919s were made without butt stocks, rear- and front sights, but the final version closely resembled the later Model of 1921. This model was designed as an automatic Colt .45 to "sweep" trenches with bullets. The New York City Police Department was the largest purchaser of the Model of 1919. Some experimental calibers aside the .45 ACP were the (11.4x23mm), .22LR, .32 ACP, .38 ACP, and 9mmP.
.351 WSL variant
Only one prototype was made in .351 WSL using a standard 20" barrel and an ROF of 1000rpm.
Thompson .30 Carbine
The layout and ergonomics of the Thompson submachine gun were also considered for the role of a Light Rifle before the adoption of the M1 Carbine. It was based on the M1921/27 variants. However, it was turned down without testing due to logistic problems.
A .30-06 variant was intended as a rival to the M1918 BAR. It had an extended receiver with a recoil buffer and fed from 20 round magazines.
The Model 1921 (M1921) was the first major production model. Fifteen thousand were produced by Colt for Auto-Ordnance. In its original design, it was finished more like a sporting weapon, with an adjustable rear sight, a blued, finned barrel and vertical foregrip (or pistol grip) and the Blish lock. The M1921 was quite expensive to manufacture, with the original retail price around $200, because of its high-quality wood furniture and finely machined parts. The M1921 was famous throughout its career with police and criminals and in motion pictures. This model gained fame from its use by criminals during Prohibition, and was nicknamed "tommy gun" by the media.
The Model 1923 was a heavy submachine gun introduced to potentially expand the Auto-Ordnance product line and was demonstrated for the U.S. Army. It fired the more powerful .45 Remington–Thompson cartridge which fired a heavier 250-grain (16.2 gram) bullet at higher muzzle velocities of about 1,450 fps (440 m/s), with greater range than the .45 ACP. It introduced a horizontal forearm, improved inline stock for accuracy, 14-inch (35.5 cm) barrel, bipod and bayonet lug. The M1923 was intended to rival the M1918 Browning Automatic Rifle (BAR) with which the Army was already satisfied. The Army did not give the Model of 1923 much consideration, so it was not adopted.
Model 1921AC (1926)
While not a new model in the usual sense of incorporating major changes, in 1926 the Cutts Compensator (a recoil brake) was offered as an option for the M1921; Thompsons with the compensator were cataloged as No. 21AC at the original price of $200.00, with the plain M1921 designated No. 21A at a reduced price of $175.00. The Model 1921 was thereafter referred to as Model 1921A or Model 1921AC, though some collectors still refer to it as the Model 1921.
The Model 1928 was the first type widely used by military forces, with the U.S. Navy and U.S. Marine Corps as major buyers through the 1930s. The original Model 1928s were Model 1921s with weight added to the actuator, which slowed down the cyclic rate of fire, a USA Navy requirement. On these guns, the model number "1921" on the receiver was updated by stamping an "8" over the last "1". The Navy Model 1928 has several names among collectors: the "Colt Overstamp", "1921 Overstamp", "28 Navy", or just "28N".
The 1928 Thompson would be the last small arm adopted by the U.S. Army that used a year designation in the official nomenclature. With the start of World War II, major contracts from several countries saved the manufacturer from bankruptcy. A notable variant of the Model 1928 with an aluminum receiver and tenite grip, buttstock, and forend, was made by Savage.
The M1928A1 variant entered mass production before the attack on Pearl Harbor, as on-hand stocks ran out. Changes included a horizontal forend, in place of the distinctive vertical foregrip ("pistol grip"), and a provision for a military sling. Despite new U.S. contracts for Lend-Lease shipments abroad to China, France, and the United Kingdom, as well as the needs of American armed forces, only two factories supplied M1928A1 Thompsons during the early years of World War II. Though it could use both the 50-round drum and the 20- or 30-round box magazines, active service showed the drums were more prone to jamming, rattled when moving, and were too heavy and bulky on long patrols. 562,511 were made. Wartime production variants had a fixed rear sight without the triangular sight guard wings and a non-ribbed barrel, both like those found on the M1/M1A1.
In addition, the Soviet Union received M1928A1s, included as standard equipment with the M3 light tanks obtained through Lend-Lease. The weapons were never issued to the Red Army because of a lack of .45 ACP ammunition on the Eastern Front; they were simply put in storage, although a picture exists of what appears to be Thompsons being used by Russian M3 Stuart crews in the Caucasus. As of September 2006, limited numbers of these weapons have been re-imported from Russia to the United States as disassembled "spare parts kits", comprising the entire weapon less the receiver (as required by Federal law).
An M1928A1 which also came with an unusual inline stock, modified with elevated sights to increase accuracy also existed.
Thompson Machine Carbine (TMC)
In 1940 Commonwealth troops in Egypt and North Africa were issued commercial model Lend-Lease Colt- and Savage-manufactured M1928s. Section leaders carried them instead of pistols or rifles. Many of the Colt models had French-language manuals packed with them as they had been abruptly diverted to England after the fall of France. They soon discovered that the weapon was prone to jamming due to sand. To fix this, the armorers removed the Blish Lock and replaced it with a hex bolt to keep the cocking handle and bolt together. The 20-round Type XX magazines had their peep-holes welded shut to keep sand out and the 50-round Type L drums were discontinued. Ammunition was scarce as it was either in small lots of Lend-Lease commercial ammo or obtained from adjacent American troops. It was later replaced by the 9mm Sten gun and Lanchester SMG.
The Japanese captured enough Thompson M1928 SMGs and ammunition when they captured Hong Kong and Malaysia that it became a limited standard weapon. It surpassed any similar weapons currently in their service. Ammunition was usually in US 42-round Lend-Lease commercial cartons or Australian 28-round military cartons captured from the Commonwealth forces that was sampled, tested, and resealed with Japanese arsenal stickers.
Models used in the Pacific by Australian troops had their sling swivels remounted on the left side to allow it to be fired more easily while prone. A metal sling mount was fitted to the left side of the wooden buttstock. Ammunition was manufactured in Australia or obtained from adjacent American troops. It was later replaced by the Owen Machine Carbine.
Responding to a request for further simplification, the M1 was standardized in April 1942 as the United States Submachine Gun, Cal. .45, M1. Rate of fire was reduced to approximately 600-700 rpm.
First issued in 1943, the M1 uses a simple blowback operation, with the charging handle moved to the side. The flip-up adjustable Lyman rear sight was replaced with a fixed L sight. Late M1s had triangular guard wings added to the rear L sight, which were standardized on the M1A1. The slots adjoining the magazine well allowing the use of a drum magazine were removed. A new magazine catch with the provision for retaining drum magazines removed, was produced, but most M1s and later M1A1s retained the original. The less expensive and more-easily manufactured "stick" magazines were used exclusively in the M1, with a new 30-round version joining the familiar 20-round type. The Cutts compensator, barrel cooling fins, and Blish lock were omitted while the buttstock was permanently affixed. Late production M1 stocks were fitted with reinforcing bolts and washers to prevent splitting of the stock where it attached to the receiver. The British had used improvised bolts or wood screws to reinforce M1928 stocks. The M1 reinforcing bolt and washer were carried over to the M1A1 and retrofitted to many of the M1928A1s in U.S. and British service. Late M1s also had simplified fire control switches, also carried over to the M1A1.
The M1A1, standardized in October 1942 as the United States Submachine Gun, Cal. .45, M1A1, could be produced in half the time of the M1928A1, and at a much lower cost. The main difference between the M1 and M1A1 was the bolt. The M1 bolt had a floating firing pin and hammer, the bolt of the M1A1 had the firing pin machined to the face of the bolt, eliminating unnecessary parts. The reinforced stock and protective sight wings were standard. The 30-round magazine became more common. In 1939, Thompsons cost the government $209 apiece. By the spring of 1942, cost-reduction design changes had brought this down to $70. In February 1944, the M1A1 reached a low price of $45 each, including accessories and spare parts, although the difference in price between the M1 and M1A1 was only $0.06. By the end of the war, the M1A1 was replaced with the even lower-cost M3 (commonly called the "Grease Gun").
The Model 1927 was the open bolt semi-automatic-only version of the M1921. It was made by modifying an existing Model 1921, including replacing certain parts. The "Thompson Submachine Gun" inscription was machined over to replace it with "Thompson Semi-Automatic Carbine", and the "Model 1921" inscription was also machined over to replace it with "Model 1927." Although the Model 1927 was semi-automatic only, it was easily converted to fully automatic by installing a full-auto Model 1921 fire control group (internal parts). Most Model 1927s owned by police have been converted back to full-auto. The original Model 1927 is classified as a machine gun under the National Firearms Act of 1934 (a) by being "readily convertible" by swapping parts and (b) by a 1982 BATF ruling making all open bolt semi-automatic firearms manufactured after the date of this ruling classified as machine guns.
The Model 1927A1 is a semi-automatic only replica version of the Thompson, originally produced by Auto-Ordnance of West Hurley, New York for the civilian collector's market from 1974 to 1999. It has been produced since 1999 by Kahr Arms of Worcester, Massachusetts. It is officially known as the "Thompson Semi-Automatic Carbine, Model of 1927A1." The internal design is completely different to operate from the closed bolt and the carbine has barrel length of 16.5 inches (42 cm) (versus open bolt operation and barrel length of 10.5 inches (270 mm) for the full automatic versions). Under federal regulations, these changes make the Model 1927A1 legally a rifle and remove it from the federal registry requirements of the National Firearms Act. These modern versions should not be confused with the original semi-automatic Model of 1927 which was a slightly modified Model of 1921 produced by Colt for Auto-Ordnance.
The Model 1927A1 is the semi-automatic replica of the Thompson Models of 1921 and 1927. The "Thompson Commando" is a semi-automatic replica of the M1928A1. The Auto-Ordnance replica of the Thompson M1 and M1A1 is known as the TM1, and may be found marked "Thompson Semi-Automatic Carbine, Caliber .45M1".
The Model 1927A3 is a semi-automatic, .22 caliber version of the Thompson produced by Auto-Ordnance in West Hurley.
The Model 1927A5 is a semi-automatic pistol version, .45 ACP version of the Thompson originally produced by Auto-Ordnance in West Hurley. It featured an aluminum receiver to reduce weight. It has been produced since 2008 by Kahr Arms of Worcester, Massachusetts as the "M1927A1 TA5".
As of changes to Federal Law (prior to 2011), the 1927A5 .45 ACP Pistol is now simply classified as a "Firearm" or "Any Other Weapon (AOW) as it neither fits the neither the definition of a Pistol or Rifle under current law.
The 1928A1 LTD is a civilian semi-automatic-only clone with fixed stock, produced by Luxembourg Defense Technology in Luxembourg.
In an attempt to expand interest and sales overseas, Auto-Ordnance entered into a partnership with and licensed the Birmingham Small Arms Company Limited (BSA) in England to produce a European model. These were produced in small quantities and have a different appearance than the classic style. The BSA 1926 was manufactured in 9mmP and 7.63mm Mauser and were tested by various governments, including France, in the mid-1920s. It was never adopted by any military force, and only a small number were produced.
Special purpose variant
A special purpose machine pistol variant of the Thompson is manufactured by RPB Industries of Atlanta.
A version with a threaded barrel for suppressors, side folding stock, and modified sights.
All variants and modified versions of Thompson Submachine Guns (even semiautomatic-only versions) are prohibited by name in Canada, as part of Prohibited Weapons Order No. 13 in 1995. Consequently, they cannot be legally imported or owned except under very limited circumstances. For example, to own one the person must be "grandfathered" and have owned one before the bill was passed against it. The submachine gun is not grandfathered like in USA, only the owner. The submachine gun can only be sold to other grandfathered individuals, this keep prices extremely low as the number of prohibited licensed individuals is very small and dwindling with time. Eventually, all prohibited guns will be confiscated.:Part 1.86
The perceived popularity of submachine guns such as the Thompson with violent gangsters in the 1920s and 1930s was one of the main reasons given for passage of the National Firearms Act by the United States Congress in 1934. One of its provisions was that owners of fully automatic firearms were required to register them with the predecessor agency of the modern Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). The law also placed restrictions on the possession, transfer, and transport of the weapons.
The possession of any fully automatic firearm is prohibited in the UK by the Firearms Act 1968; prohibited firearms can be possessed on a section 5 certificate, but these are not issued to civilians. A fully automatic firearm that has been converted to semi-automatic fire, such as the Model 1927, is prohibited by the Firearms Act 1988 as, also, is any centre fire purpose made semi-automatic weapon such as the Model 1927A1. It is now effectively impossible for a firearm of this type to be legally possessed by a member of the general public.
- Albania: Used Chinese produced copies during the cold war era.
- Australia: Used by Australian forces during WWII until it was replaced by the Australian-made Owen submachine gun.
- Brazil: Used by the Brazilian forces during WWII and after the war, until the mid 1980s 
- British India: Widely used by the Indian Army in the Malayan Campaign and Burma Campaigns
- Dominican Republic
- People's Republic of China: Limited, sometimes unlicensed copies
- Republic of China
- Greece: Used by Greek armed forces, resistance fighters, Gendarmerie and police units during World War II and immediately postwar.
- Indonesia: Examples captured from Dutch forces were used during the Indonesian National Revolution and later by Indonesian Army Special Forces in 1950–70s
- Ireland: 123 used by the Irish Defence Forces during the Emergency and widely used by the IRA
- Italy: Captured examples pressed into use by the Italian Army prior to September 8, 1943. Also supplied to partisans and to the Italian Co-belligerent Army. After the war, it was mostly issued to Italian Air Force troopers and the Carabinieri.
- Japan: Used in some quantities by the Japanese Maritime Self-Defense Forces
- Republic of Korea: Limited received U.S government used at Korean War, Vietnam War. After the Vietnam War, all Thompson SMGs were scrapped.
- Luxembourg: M1A1 in service 1952-1967, replaced by Uzi.
- The Netherlands: In early World War II, at least 3,680 Thompsons acquired through Lend-Lease
- New Zealand
- North Vietnam: Unlicensed copies. Used by North Vietnamese soldiers in the First Indochina War
- Poland: Used by Polish Armed Forces in the West during WWII (bought from British Army) and by resistance fighters during Warsaw Uprising (American supply drops)
- Portugal: Small number bought for police use, designated m/1928
- South Vietnam
- Soviet Union
- Turkey: Used between 1950s–1970s, saw action in Korean War and 1974 Cyprus War
- United Kingdom. First issued to the GHQ Liaison Unit ('Phantom' )in February 1940, in advance of main War Office contracts.
- United States: Employed by the United States Marine Corps and by the United States Army 1938, including paratroops in World War II.
- West Germany: Used post World War II; Received by the U.S government and captured by Nazi Germany.
- American organized crime syndicates, such as the Chicago Outfit and American Mafia.
- The Provisional IRA used the 1921 variant, mainly during the early 1960s to 1970s.
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- Uzi Eilam, Eilam's Arc: How Israel Became a Military Technology Powerhouse, Sussex Academic Press (2011) p. 7
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- As mentioned in a notorious reportage on the death of outlaw Salvatore Giuliano:http://www.ilcassetto.it/notizia.php?tid=148
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