Project of an automatic rifle based on a Thompson M1 machine gun.
February 24, 201631
Creating a new small weapon based on existing samples: a common and proven practice that promotes progress and allows you to upgrade your arsenals without any difficulty or special cost. In this case, the prototype product and the new model almost always belong to the same class: rifles are made on the basis of rifles, and pistols become the basis of new pistols. Attempts are also being made to rework the weapons with the transfer to another class, but they are not always successful. For example, in the early 1940s, American gunsmiths tried to create a promising automatic rifle with a Thompson M1 machine gun, but the result was not suitable for anyone.
In 1942, the Thompson Type M1 machine gun entered 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. At the end of 42, a new weapon modification called the M1A1 appeared. It differed from the basic M1 in an even simpler design. Its main difference was the fixed drummer, which allowed firing only in automatic mode. The simplicity and low cost (compared to the “Thompsons” of the previous models) made it possible for several years to launch more than 820 thousand machine guns of two modifications. In addition, there was a proposal to create more powerful weapons based on existing developments.
In about 1942 or 1943, it was proposed to rework the Thompson M1/M1A1 machine gun design to use the new cartridge. A potential gun display was supposed to use standard Springfield rifle-type ammunition (30-06 Springfield) (7.62x63mm). Thus, the result of the project was the emergence of a new automatic rifle, created on the basis of a machine gun.
The only known photo of a rifle at the base of a Thompson machine gun. Photo Strangernn.livejournal.com
Probably one of the main objectives of the new project was the creation of new small arms for a rifle cartridge with the lowest possible price for production and operation. The “military” modifications of the Thompson machine gun differed from earlier versions by a less complex design and higher low-cost production. It is possible that it was these weapon advantages that were planned to be used in the project of a new automatic rifle.
The new automatic rifle was reportedly an enlarged base machine gun with some design changes associated with the use of a more powerful cartridge. The most notable 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 made to the internal units, which, in particular, affected the distance between the store’s receiving window and the activation mechanism.
The general architecture and design of the preserved weapons. The main unit of the rifle was an oblong receiver of rectangular section, in front of which the barrel was attached. To protect the hands of the heated trunk shooter in front of the box, he was provided with a wooden forearm. If the standard stem of the M1/M1A1 machine gun was used when assembling the test rifle, then it can be argued that the new weapon received a barrel three times as long. On the lower rear of the receiver the trigger frame was adjusted with elements of the firing mechanism, trigger and pistol grip. A characteristically shaped wooden end was also attached to the main plate of this unit.
It was proposed that the supply of .30-06 ammunition be made from standard detachable box magazines with a 20-round capacity. The tent was borrowed from the BAR M1918 Browning Automatic Rifle. As conceived by the authors of the new project, the tent should be placed in a large window at the bottom of the receiver, expanded with cutouts on its side walls. To safely store the tent in 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 together actually served as a receiving hub, but they were simpler and easier.
The increase in receiver size, compared to the basic machine gun, was associated with the use of a new, more powerful cartridge and the use of reworked automation. Like the prototype, the automatic rifle was supposed to work on the principle of the free shutter. Due to the high power of the cartridge, gunsmiths had to weigh the bolt, redo the extractor and other parts that interact with the cartridge, and also make other adjustments. In particular, a more powerful and longer return spring was needed.
The spring associated with the free door 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 back cover. The back of the spring would be located inside a cylindrical housing placed on the back wall of the receiver.
As before, it was suggested that the gun be cocked with the help of a per-pole shooter.No, it was taken out through a slot in the right wall of the receiver. The groove had a longer length, which was due to the dimensions of the .30-06 cartridge and the large stroke.
The trigger mechanism was taken from the base machine gun with minimal modifications that were associated with other bolt dimensions and some other features of the new weapon. At the same time, the overall design of the control system and the location of the controls were retained. Then, to the left above the pistol grip were two control levers. One was responsible for locking the trigger, the other, to choose the firing mode.
It should be noted that there is no exact data on the sample of the prototype from which the rifle was built. If the automatic rifle was based on the design of a Thompson M1 machine gun, then it should have been a trigger with the possibility of simple, automatic firing. In this case, the shutter had to be equipped with a separate mobile drummer, actuated by a shutter release. 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 only be fired in bursts and consequently had only one lever controlling 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 Thompson-based automatic rifle project was to adapt 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 feeder, the cartridges from the tent had to go up the disassembly line, after which the spring-loaded door had to send them to the chamber. With the help of a shutter release (or a fixed drummer), a shot was fired, after which the shutter was pushed back, removing and discarding the cartridge. In the rearmost position, the shutter was either caught with a fastener or moved forward again, producing the next shot.
In 1942-43, at least one prototype of a promising automatic rifle was manufactured. This weapon had a rather simple design, associated with the experimental nature of the project. For this reason, serial elements made of wooden accessories were used: handle plates, fenders and stock. In addition, the test rifle was not equipped with any sights.
Probably, the authors of the project initially understood the prospects of this development, which could hardly be considered a good one. This project had notable problems of a different nature. First, because it was based on a dubious concept. Such features led the development to the corresponding result.
Thompson M1 submachine gun. Photo from Wikimedia Commons
Exact data on the course of testing and the displayed characteristics of an automatic rifle based on a machine 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. Therefore, the initial velocity of the bullet could exceed 800-850 m/s, and the effective firing range can be evaluated at 800-1000 m. Naturally, the actual characteristics of the weapon, especially in real combat conditions, could be different.
It only remains to guess what kind of rate of fire the automatic rifle, built on the basis of a free shutter and using a powerful .30-06 Springfield cartridge, could display. 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.
The .30-06 cartridge reportedly provides a bullet energy of at least 3800 J. Depending on the type of bullet, this parameter can reach J.4000-4050. It’s not hard to imagine the recoil force of such a weapon, especially when fired in automatic mode. The use of such a powerful cartridge simply did not allow the use of a new rifle to be trusted as a complete weapon for the 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 triggering characteristics of both samples could be at the same level. Moreover, apparently, the list of drawbacks was the same. Thus, the large power of the cartridge seriously complicated the firing of bursts in a standing position, and the use of weapons such as light machine gun was hampered by the small capacity of the tent and other design features.
The project for an automatic rifle based on a machine gun has reportedly reached the stage of assembling a prototype and its subsequent testing. After that, all work was stopped. The new weapon had no decisive advantages over existing samples, but it did not differ from them in its shortcomings. The mass production and exploitation of such weapons was pointless. The project was shut down due to lack of prospects. The subsequent fate of the manufactured prototype (or prototypes) is unknown.
It can be argued that the main problem with the project for an automatic rifle based on the “Thompson” was the cartridge selected. The designers decided to use .30-06 Springfield rifle ammunition, which ultimately affected the characteristics of the weapon. Already in the first half of the 1940s, it became clear that the continued use of existing cartridges does not solve all current problems. For the further development of small arms, new ammunition is required. The result was the appearance of new intermediate cartridges, which became the next impetus for weapons development. The concept of an automatic rifle for a rifle cartridge was not completely rejected, but was later implemented in other ways and on a different technological level.
