In 1942, the M1-type Thompson submachine gun went into the series. It was a modified and simplified version of the M1928 weapon with a number of innovations aimed at cheaper production and mass exploitation. By the end of 42, a new weapon modification called M1A1 appeared. It differed from the basic M1 in an even simpler design. Its main difference was the fixed drummer, which allowed to shoot only in automatic mode. The simplicity and low cost (in comparison with the “Thompsons” of the previous models) allowed for several years to release more than 820 thousands of submachine guns of two modifications. In addition, there was a proposal to create more powerful weapons based on existing developments.
Approximately in 1942 or 1943, it was proposed to rework the design of the Thompson M1 / M1A1 submachine gun to use the new cartridge. A prospective weapons sample was supposed to use standard .30-06 Springfield type rifle ammunition (7,62x63 mm). Thus, the result of the project was to be the emergence of a new automatic rifle, created on the basis of a submachine gun.
The only known photo of a rifle at the base of a Thompson submachine gun. Photo Strangernn.livejournal.com
Probably one of the main goals of the new project was the creation of a new small arms for a rifle cartridge with the lowest possible price for production and operation. The “military” modifications of the Thompson submachine gun differed from earlier versions by a less complex design and greater low cost production. It is possible that it was these weapons advantages that were planned to be used in the project of a new automatic rifle.
According to reports, the new automatic rifle was an enlarged base submachine gun with some design changes associated with the use of a more powerful cartridge. The most noticeable result of such innovations was a change in the dimensions and proportions of the weapon. A relatively long barrel appeared, and the size of the receiver increased. Some improvements have been applied to the internal units, which, in particular, affected the distance between the store's receiving window and the trigger mechanism.
The overall architecture and layout of weapons preserved. The main unit of the rifle was an oblong receiver of rectangular section, in front of which was attached the barrel. To protect the hands of the shooter from the heated trunk in front of the box was provided a wooden forearm. If the standard shank of the M1 / M1A1 submachine gun was used when assembling the test rifle, then it can be argued that the new weapon received about three times longer barrel. In the rear lower part of the receiver was fastened trigger frame with elements of the firing mechanism, trigger and pistol grip. A wooden butt of characteristic shape was also attached to the main plate of this unit.
The supply of ammunition .30-06 was proposed to be carried out from standard detachable box magazines with a capacity of 20 cartridges. The store was borrowed from the BAR M1918 Browning Automatic Rifle. As conceived by the authors of the new project, the store should be placed in a large window at the bottom of the receiver, expanded with cut-outs in its side walls. To securely store the shop in its place, in front of and behind the window, U-shaped restraints were provided, one of which contained a latch. The two parts that held the store actually served as a receiving shaft, but they were simpler and easier.
The increase in the size of the receiver, in comparison with the basic submachine gun, was associated with the use of a new, more powerful cartridge and with the use of reworked automation. Like the prototype, the automatic rifle was supposed to work using the principle of the free shutter. Due to the high power of the cartridge, gunsmiths had to weight the bolt, redo the extractor and other parts that interact with the cartridge, and also make other adjustments. In particular, a more powerful and long return spring was needed.
The spring associated with the free gate with the required parameters was so long that it was necessary to increase the dimensions of the receiver, and also to equip it with an additional rear cup-casing. The back of the spring was to be located inside a cylindrical housing placed on the rear wall of the receiver.
As before, it was suggested that the weapon be cocked with the help of a bolt handle, pulled out through a slot in the right wall of the receiver. The slot had an increased length, which was due to the dimensions of the .30-06 cartridge and the large stroke.
The trigger mechanism was borrowed from the base submachine gun with minimal modifications that were associated with other dimensions of the bolt and some other features of the new weapon. At the same time, the general layout of the control system and the location of the controls were maintained. So, on the left above the pistol grip were two-way control levers. One was responsible for blocking the trigger, the other - for the choice of fire mode.
It should be noted that there are no exact data on the prototype sample on the basis of which the rifle was built. If the automatic rifle was based on the design of a Thompson M1 submachine gun, then it should have been a trigger with the possibility of single and automatic fire. The shutter in this case was to be equipped with a separate movable drummer, driven by a trigger. The submachine gun of the M1A1 version was distinguished by the absence of a trigger and a fixed drummer rigidly fixed on the bolt. This modification of the weapon could fire only in bursts and, accordingly, had only one control lever of the firing mechanism. If the automatic rifle was based on a product like the M1A1, then it should have inherited the corresponding traits.
One of the main goals of the project of an automatic rifle based on the Thompson was the adaptation of the existing automation to a new cartridge. Thus, the basic principles of the two weapons were the same. Under the action of the spring and the feeder, the cartridges from the store had to climb the dismounting line, after which the spring-loaded gate had to send them to the chamber. With the help of a trigger (or a fixed drummer), a shot was made, after which the shutter was rolled back, removing and discarding the cartridge. In the rearmost position, the shutter was captured with a sear or went forward again, producing the next shot.
In the 1942-43, at least one prototype of a promising automatic rifle was manufactured. This weapon had a fairly simple design, associated with the experimental nature of the project. For this reason, ready-made serial elements of wooden fittings were used: handle plates, forend and stock. In addition, the test rifle was not equipped with any sights.
Probably, the authors of the project initially understood the prospects for this development, which could hardly be called good. This project had noticeable problems of a different nature. First of all, due to the fact that it was based on a dubious concept. Such features led the development to the corresponding result.
Exact data on the course of the tests and the shown characteristics of an automatic rifle based on a submachine gun are not available. It can be assumed that a relatively powerful cartridge could provide basic characteristics at the level of a BAR rifle or other types of weapons of a similar class chambered for .30-06. Thus, the initial speed of the bullet could exceed 800-850 m / s, and the effective firing range can be assessed in 800-1000 m. Naturally, the actual characteristics of the weapon, especially in real combat conditions, could be different.
It remains only to guess what kind of rate of fire could show automatic rifle, built on the basis of a free shutter and using a powerful cartridge .30-06 Springfield. This figure probably reached at least 400-500 rounds per minute or more. One way or another, a high rate of fire should have a negative effect on the overall effectiveness of the new weapon.
According to reports, the .30-06 cartridge provides a muzzle bullet energy of at least 3800 J. Depending on the type of bullet, this parameter can reach J. 4000-4050. It is not difficult to imagine the recoil force of such a weapon, especially when shooting in automatic mode. The use of such a powerful cartridge simply did not allow to rely on the use of a new rifle as a full-fledged weapon for infantry.
From the point of view of the applied cartridge, an automatic rifle based on the Thompson could be a direct competitor to the BAR M1918 product, which differs from it in its lower price and design complexity. On this, however, the advantages over existing weapons ended. The main shooting characteristics of both samples could be on the same level. In addition, apparently, the list of drawbacks was the same. Thus, the large power of the cartridge seriously complicated the firing of bursts in the standing position, and the use of weapons as a light machine gun was made difficult by the small capacity of the store and other design features.
According to reports, the project of an automatic rifle based on a submachine gun reached the stage of assembling a prototype and its subsequent tests. After that, all work was stopped. The new weapon did not have any decisive advantages over the existing samples, but did not differ from them by its shortcomings. Mass production and exploitation of such weapons did not make sense. The project was closed due to the lack of prospects. The subsequent fate of the manufactured prototype (or prototypes) is unknown.
It can be argued that the main problem of the project of an automatic rifle based on the "Thompson" was the selected cartridge. The designers decided to use rifle ammunition .30-06 Springfield, which ultimately affected the characteristics of the weapon. Already in the first half of the forties, it became clear that the continued use of existing cartridges does not allow solving all current problems. For the further development of small arms required new ammunition. The result was the emergence of new intermediate cartridges, which became the next impetus for the development of weapons. The concept of an automatic rifle for a rifle cartridge was not completely rejected, but was later implemented in other ways and at a different technological level.
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