John T. Thompson founded the Auto Ordnance Corp. in 1916, and began his developments in submachine guns with purchase of John Blish patent (1915), that described a delayed blowback automatic firearm. This patent described delayed blowback breech system in which a sloping metal wedge interlocked the breech block with the gun body.
Under high pressure, as when the cartridge fired, the angle of the slope was such that the mating faces jammed solid. As the pressure dropped, the faces were able to slip across each other, the wedge moved up due to the slope, and the breech unlocked. This idea was used in all Thompson submachine guns except for M1 and M1A1 (those were simply blowback operated).
The first Thompson experimental submachine gun appeared in 1919, and first production model appeared in 1921; it was manufactured under contract by Colt Firearms Manufacturing Co, as well as later M1928 models. Production of M1928A1 and M1 submachine guns was carried out by Auto-Ordnance and Savage, and some licensed copies were manufactured by B.S.A. in Great Britain.
There also were some submachine guns that never reached full-scale production, such as "Military model" M1923, which was developed with intent to extend the effective range out to 600 yards (approx 550 meters). To achieve this goal, M1923 was chambered for a special .45 Remington-Thompson ammunition, which fired heavier 250-grain (16,2 gram) bullet (as opposed to standard 230-grain .45ACP bullet) at higher muzzle velocities of about 1450 fps (440m/s). This weapon also had longer barrel, and optional bipod and bayonet mount. It was tested but never produced in any significant numbers. The other rare version was the original Model 1927, which was a semi-automatic only version of Model 1921.
Thompson M1A1
The first Thompson gun to see some military use was Model 1928, used by US navy during its expedition in Nicaragua. The so-called "Navy" model 1928 was distinguished by a horizontal forearm that replaced the front grip, and by added sling swivels. With the start of World war 2, US Army procured a large number of Model 1928 submachine guns in "Navy" configuration, marked as US Model 1928A1. These weapons were rather expensive to make, and in 1942 Army adopted a simplified version of M1928A1, known as M1. A little later, an M1A1 version was adopted, which further simplified the design by adoption of a fixed firing pi; otherwise M1A1 were similar to M1 submachine guns. Thomson submachine guns served in US Army well into the Vietnam era, although in limited numbers. American police used Thompson guns until 1970s or 1980s, and few still could be found in some police armories in USA and several other countries of the world.
Thompson submachine guns were widely exported commercially prior to and after WW2; Many guns were supplied to Britain and USSR through Lend-lease program during WW2. It must be noted that Soviet troops generally not liked Tommy guns, because of excessive weight and lack of bullet penetration, compared to 7,62mm submachine guns such as PPSh-41 or PPS-43.
Thompson M1921 and M1928 submachine guns were delayed blowback operated, selective fired weapons, based on Blish principle. Blish patent described a delayed blowback breech system in which a sloping metal wedge interlocked the breech block with the gun body. Under high pressure, as when the cartridge fired, the angle of the slope was such that the mating faces jammed solid. As the pressure dropped, the faces were able to slip across each other, the wedge moved up due to the slope, and the breech unlocked. The wartime M1 and M1A1 submachine guns used simple blowback action. All Thompson submachine guns fired from open bolt. The cocking handle was located on the top of receiver on Models of 1921 and 1928, ad on the right side of the receiver on models M1 and M1A1. Separate manual safety and fire mode selector levers were located on the left side of receiver, above the trigger. Barrel was usually partially finned, and on model 1928, fitted with so-called Cutts compensator (not present on M1 and M1A1). Feed was from double-row box magazines containing 20 or 30 rounds, or drum magazines holding 50 or 100 rounds. Box magazines were inserted into the magazine slot from below; drum magazines were inserted into the same slot from the side. Drum magazines were not available for M1 and M1A1 submachine guns.
Furniture included pistol grip, detachable wooden shoulder stock and either a detachable forward grip or a horizontal forearm. Sights on pre-war models included front blade and protected rear, which combined a fixed open-notch blade and raising diopter, which was adjustable for both windage and range (up to 500 yards). Wartime models (M1928A1, M1 and M1A1) used a simple fixed aperture (diopter) rear sight, with or without protecting side "ears".
At the present time, Kahr Arms makes a variety of "Tommy-guns" under Auto Ordnance trade mark. These weapons are limited to semi-automatic fire only and usually have longer barrel to conform to US laws.
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