Thompson submachine gun, model M1A1
The **Thompson submachine gun**, also known as the **Tommy gun**, was an early submachine gun design. It was popular among soldiers, police, and civilians alike. It was invented by Brigadier General John T. Thompson at the end of World War I as a "trench-boom" weapon, or a weapon that could clear out trenches very quickly. The war ended before the submachine gun could be used in battle. In 1919, Brigadier General Thompson had the company he founded, Auto-Ordnance Company, modify the gun for civilian use. The gun was classified as a submachine gun, meaning a small, fully automatic, hand-held gun that fires pistol ammunition. It remains an iconic firearm that is very popular with collectors. It fires .45 ACP caliber bullets, an effective and accurate combat bullet against human targets.

Technical specification
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* **Caliber:** .45 ACP
* **Barrel:** 10.5 inches (270 mm)
* **Length:** 32 inches (810 mm)
* **Weight:** 10 pounds (4.5 kg) empty
* **Operation:** friction delayed gas blowback
* **Capacity:** 20, 30 round straight box magazine, 50, 100 round drum magazine (not compatible with M1 or M1A1), belt feed ("Persuader" prototype)
* **Type:** Submachine gun
* **Fire modes:** Semi-auto/Full-auto (600-725 RPM, 1,500 RPM on "Annihilator 1" prototype, and 800 on "Annihilator 2")
* **In service:** M1919 prototypes: *(1919 - 1920)*/Serial production *(1921 - present day)*

History
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In 1882, John T. Thompson entered the United States Army. During the Spanish–American War he made a reputation for himself making sure ammunition got to the front lines. This was at a time of almost complete chaos in the army supply system. He later played a part in developing two important American military weapons. These were the M1903 Springfield rifle and the M1911 pistol. In 1916 Auto-Ordnance was started with Thompson holding the majority of shares. Designed for use in World War I, the gun was first called "The Annihilator I" (Thompson nicknamed it a trench broom) could fire 20 rounds per second. The first cases of the new submachine gun arrived on the docks for shipment on November 11, 1918; the same day the war ended. Thompson and Auto-Ordnance began developing the gun for civilian markets. In 1921 the first model, called the M1921, was produced.

After World War I
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In 1921, the Colt Patent Firearms Company made 15,000 Thompson submachine guns for Auto-Ordinance at a cost of $38.25 each. These were called the "Model 1921A". This model weighed 10.25 pounds (4.65 kg) and had an effective range (distance it was accurate) of 164 feet (50 m). General Thompson tried to sell his gun to European countries with little success. He tried selling it in the US but sales were slow. In 1926 he got orders from the United States Postal Service and the United States Marine Corps. The Marines used the guns during the Banana Wars. It worked well to counter ambushes by Nicaraguan guerrillas. The Irish Republican Army used them in 1921 during the last part of the Irish War of Independence. They were not impressed by the fact they could only kill about 32 percent of those they fired at. Others who bought his submachine gun included Law enforcement agencies and ranchers. Organized crime quickly found uses for the gun. Later, the United States Navy ordered 1,500.

World War II
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The US military began using the weapon in 1938 and used it throughout World War II. There were two variants used. The model M1928A1 could use either stick or drum magazines, it had a muzzle brake (to counter the gun's tendency to rise when fired) and had Cooling fins (to counter the barrel of the gun getting too hot). The M1A1 model had no cooling fins, could only use the stick magazines and had a simplified sight. It was used by all the allies during the war. The main problem of the Thompson submachine gun was it was complex and expensive to manufacture. It was also heavy at about 14 pounds (6.4 kg) loaded. It had to be kept very clean or it would misfire. But soldiers liked the weapon. It was a favorite of British and Australian soldiers. In the US military it was carried by squad leaders and officers. In the heavy jungles in the Pacific War, it sounded dangerously like the Japanese light machine guns causing some confusion on both sides. When the US developed the M3 submachine gun, also called the "grease gun", it was much lighter, cheaper to make and had a slower rate of fire. Most soldiers who had Thompsons were very slow to give them up in favor of the less well-liked grease gun. 

It was used during the Korean War and later during the Vietnam War. The Thompson submachine gun was retired in 1971 after 33 years of service.

Other militaries
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The Thompson was used in the Arab–Israeli conflict, the Cuban Revolution and in the Northern Ireland conflict (1969–1998. The gun continues to be produced today, with many countries around the world still using it. Over 1,700,000 Thompson submachine guns have been made.

Other websites
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Wikimedia Commons has media related to ***Thompson submachine gun***.

* From Gangland to the Battlefield — 15 Amazing Facts About the Thompson Submachine Gun
* Why do the earlier Thompson submachine guns have drum magazines ...
* Firing a Thompson on full-auto, YouTube