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Thompson M1A1
Credits: The Unofficial Tommy Gun Page, www.sproe.com/T/t-thompson-smg.htm

The Thompson submachine gun was a semi- or fully-automatic delayed blowback weapon. Known as the "Tommy Gun", the weapon was originally designed by General John Thompson for use in World War I, but prototype designs built by Auto-Ordnance Corporation were completed just as the war ended. With the military fairly uninterested in the weapon, the Thompson was marketed at the general public, and eventually became a well-known weapon for criminals in the 1920's and 1930's.

General Thompson

In 1938 the U.S. Army adopted the Thompson as a weapon and it was given the M1928A1 designation. A variant of the M1928 model, the M1928A1 used a horizontal foregrip instead of a vertical foregrip, and made use of box magazines instead of drum magazines. The 50-round drum magazine was prone to jamming and was not well suited to combat conditions.

Updates to the weapon were made over time in order to simplify its production, and in April of 1942 the M1 model of the Thompson replaced the older M1928A1. Among the changes made were a permanently attached buttstock, and design alterations that prevented the use of the drum magazine. By October of 1942 the M1 was replaced by the M1A1, which removed the M1's firing pin and hammer and replaced it with firing pin machined into the face of the bolt. Production of the M1/M1A1 during World War II was accomplished by Auto-Ordnance Corporation and Savage Arms Company, who produced 847,991 and 539,143 copies of the weapon respectively. The Thompson was a reliable and well-respected weapon, with its major drawbacks being its significant weight and limited range.

The M1A1 was eventually replaced by the M3 submachine gun. The M3 was significantly cheaper to manufacture and went into service in 1944. Although no longer an actively supplied weapon, the Thompson would continue to serve the Army through Korea and, in limited use, Vietnam.

Technical Data
.45 ACP
Operation Full auto and single shot
Length 33 3/4"
Barrel length without Cutts compensator 10 1/4"
Barrel length with Cutts compensator 12 1/2"
20 or 30 round box magazine
50 round drum magazine
Foresight blade
Back sight adjustable slide on leaf graduated 50-600 yards
Open battle sight (aperture in position with leaf lowered) sighted for 50 yards
Weight of gun with drum magazine, loaded

50 rounds:  14 3/4 lbs
Weight of gun with box magazine, loaded
20 rounds:  11 1/4 lbs
30 rounds:  11 3/4 lbs
Cyclic Rate of fire 700 rpm

A Marine in Okinawa uses his Thompson M1A1

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