Thompson Submachine Gun, Cal .45, M1A1

Commonly called the "Thompson." The M1A1 was an evolution of the M1928, M1928A1, and M1 Thompsons which also saw service with the US Army.

The Thompson was very popular with the troops, but was heavy for a submachinegun, and many feel it was overly complicated.

The M1A1 is a much simpler weapon than the earlier models, but was still difficult and expensive to manufacture.

John T. Thompson who helped develop the M1903 Springfield rifle and M1911 .45 caliber pistol, began work on a "trench broom" for close quarter combat shortly after his retirement from 
the Army in 1918. He recognized that the .45 caliber slug used in the M1911 pistol would be devastating when used in a fully automatic weapon.

By the spring of 1920 Thompson's company (Auto-Ordnance) produced a prototype capable of firing 800 rounds a minute.

Despite its excellent test performance, the Thompson was not adopted for use by either the US Army or Marine Corps. Still, Thompson contracted with Colt for the manufacture of 15,000 
guns, designated "Thompson Submachine Gun, Model of 1921". The 15,000 guns manufactured by Colt lasted until the eve of World War II. In 1940, the U.S. Army ordered 20,000 
Thompson submachine guns; in 1941 the Army ordered an additional 319,000.

One of the main assets of the Thompson submachine gun was reliability; it performed better than most submachine guns when exposed to dirt, mud and rain.

The main complaints against the Thompson were it's weight, inaccuracy at ranges over 50 yards, and lack of penetrating power.

Operation Selective fire (fully and semi-automatic)

Caliber .45 (11.4 mm)

Muzzle velocity 280 mps (920 fps)

Ammunition .45 ACP, 230 gr bullet, 5 gr charge

Capacity Thompson (M1928A1): 50-round drum &20- and 30-round
detachable box magazine.

M1 and M1A1: 20-and 30-round detachable box magazine

Weight 4.9 kg (11 lbs)

Overall length 85.6 cm (33.7 in)

Rate of fire 600 to 725 rpm

Effective range 50m (55yds)

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