The Thompson submachine gun, which was very popular with American gangsters, is well known, but there is much less information about the self-loading rifle developed by John T. Thompson’s Auto-Ordnance in 1922. This is most likely what Colt and Auto-Ordnance representatives thought when they learned that their rifles had lost the competition for a promising self-loading rifle held by the American military in 1921. Having quickly teamed up (the companies already had experience in joint developments while refining the Thompson submachine gun), they already in 1922 (the competition was still in effect) offered the American military a new version of a self-loading rifle chambered for the .30-06 (7.62x63 mm) army cartridge
The basis of the rifle’s automatic operation was a delayed breech (semi-free breech), developed by John Blesh. This breech worked on the principle that at the moment of high pressure in the chamber, the inclined surfaces of the breech and the receiver, which are in engagement, have a maximum coefficient of friction and cannot move relative to each other, but after the pressure drops, the coefficient of friction drops, and these inclined surfaces can begin to move. This principle was used on the Thompson submachine gun, and, without further ado, the designers of “Auto-Ordnance” transferred it to the self-loading rifle: on the rear part of the rifle’s breech there were two rows of six lugs (with an inclination of 85 degrees), which, when the breech was closed, touched the same rows of cutouts in the receiver. At high pressure they “stuck” together and the bolt remained locked, and after the pressure dropped, the locking lugs began to slide, the bolt unlocked and moved back, compressing a powerful return spring. Moving back, the bolt cocked the striker and ejected the spent cartridge. Moving forward, it fed a new cartridge and locked the chamber. At the rear of the receiver there was a flag safety (like the Mauser). The rifle used a 5-round magazine. A 20-round magazine was developed for it a little later
The rifle was unlucky, although it all started quite promisingly. The Thompson and Colt weapons presented for the 1921 tests, although they received a number of comments, were nevertheless ordered in April 1922 by the then Chief of the US Army Ordnance Department in the amount of 20 units. But on the condition that all the comments would be taken into account. The American army received the ordered batch of rifles only in 1925. Apparently, the designers were busy “finishing” the rifle. The weapon was sent for military tests in several parts, during which several problems were identified. The first problem with the rifle was that for normal operation of the automatic system, it required pre-lubricated cartridges. For this purpose, special felt pads were installed in the lower part of the receiver near the magazine window, which had to be changed periodically. The second problem with the rifle was ejected cartridges: during tests, they flew out of the rifle with such force that they posed a danger to those nearby. The accompanying problems include the excessively long receiver required for such a bolt (together with the barrel 129 cm) and, accordingly, the noticeable weight of the weapon (up to 5 kg). And, of course, the shooter was not very happy about the fact that the receiver was too close to his face.
Nevertheless, Auto-Ordnance and Colt did not change anything: almost the same version of the Thompson and Colt self-loading rifle was presented for the new stage of testing, which took place in 1929. The main difference was the caliber - .276 (7 mm) instead of .30 (7.62 mm). The rifle lost these tests and, based on their results, American specialists chose the Pedersen and Garand rifles for further development.
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