Science Fair Project Encyclopedia
Thompson submachine gun
The Thompson submachine gun, also known as the Tommy gun, was an American submachine gun (SMG) that became infamous during the Prohibition era. It was a common sight in gangster films of the time, being used both by criminals and by law enforcement officers. The "Tommy gun" was also known as the "Chicago typewriter" and was favored for its compact size and high volume of automatic fire.
Developed during World War I by General John T. Thompson, the Thompson was designed to use the .45 ACP (Automatic Colt Pistol) cartridge, and was used by the U.S. Army and British Commandos during World War II. The operating mode of most Thompsons is direct blow-back, although early models used the Blish lock, turning the mechanism into a delayed blow-back system. After WWII it saw limited service in Korea, and was carried unofficially by a few soldiers in Vietnam.
The Thompson design went through several changes while in military service during WWII, almost all directed at reducing production cost and manufacturing time. It was eventually replaced mid-war with the M3 "Grease Gun".
In the United States, it was used by law enforcement, most prominently the FBI, until 1976 when it was declared obsolete. All Thompsons in U.S. government possession were destroyed, except for a few token museum pieces and training models.
Due to its gangster-era and WWII connections, Thompsons are highly sought-after collector's items. An original 1928 gun in working condition can easily fetch $15,000. Semi-automatic replicas are currently produced by the Auto-Ordnance Company (a division of Kahr Firearms.)
Approx. 1,700,000 of these weapons were produced, 1,387,134 of them being the simplified WWII M1 variant.
The original design, it is fashioned more like a sporting weapon. It was quite expensive to make, with high-quality wood furniture and finely-machined parts.
The semi-auto only version of the M1921.
The M1928 only differed slightly from the M1921, having a lower rate of fire due to its use of heavy actuators and less powerful recoil springs.
The model available during the early years of WWII, the M1928A1 was faster and cheaper to manufacture than the M1928. The most visible difference between the two models is the removal of the vertical grip in favour of the horizontal one. Though the weapon could use both the 50- or the 100-round drum as well as the 20- or 30-round magazines, it was found that the drums were more prone to jamming.
A result of further simplification to cut costs, the most notable difference between the M1 and the M1928A1 is the inability of the M1 to utilize the ammunition drum. The less-expensive and easily-manufactured 20- and 30-round "stick" magazines were exclusively used in this version. It also has a permanently-attached buttstock and was first issued in 1943.
Caliber: .45 ACP
Mass, empty: 4.78 kg
Barrel Length: 267 mm
Rate of Fire: 700 RPM
Capacity: 20/30 rounds box magazine
A very slight difference from the M1, the M1A1 had the firing pin machined into the face of the bolt.
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