… Unlike many other designs, the Kalashnikov assault rifle does not pre-shift the sleeve when the bolt is turned. Because of this … an extremely large ejector hook is required. Peter J. Cocalis.
After firing, at the initial stage of the recoil of the bolt carrier, the bolt continued to remain locked. The bolt carrier moved alone, choosing a free stroke when rolling back … At the same time, a preliminary "straining" of the cartridge case in the chamber took place …
… Thus, the sleeve, pressed by the ejector hook to the mirror of the bolt cup, was turned in the chamber … S. B. Monetchikov, History of the Russian automatic machine.
… The designer Kalashnikov invented the release of the sleeve to reduce delays during firing. You see, during a shot, the powder gases inflate the sleeve, and it can jam. And in the "Kalash" there is a hook, which, as it were, pulls the sleeve off before being ejected, jerks off the spot, and then it is easily extracted. But this is the problem of the technology of the production of cartridges! A. Kuptsov.
… let's move on to the Kalashnikov assault rifle, in it the slots for the latch stops in the receiver liner are also made at an angle, in addition, bevels are made at the corners of the lugs to facilitate the movement of the stops in the cutouts. This solution, when the shutter is locked, allows the dirty or damaged sleeve to be "squeezed", and during extraction it allows a preliminary shift with great effort. How it works? After the shot, the frame turns the bolt, and after about half of the turn, the bolt begins to move back simultaneously with the rotation due to the inclination of the notches, and here the rotational movement is converted into a displacement back with great effort (screw press principle). Thought stream of the near-weapon hamster.
Striking
And laughter and sin. Sleeve shredding has been used since the invention of the unitary rifle cartridge in bolt-action weapons. Its essence is as follows. After firing, the sleeve is sealed to the chamber walls with such force that it cannot be pulled out with a simple longitudinal movement. When the bolt is turned, after disengaging the lugs, it rests with some protrusion against a curved or oblique cut at an angle of 70-80 degrees to the axis of the weapon on the receiver liner or the box itself. In this case, a lever is formed between the large angle of rotation of the shutter and its small displacement in the longitudinal opening direction. Due to such a lever, this displacement occurs with a much greater force on the sleeve and less on the bolt handle, and this, in turn, facilitates its extraction. After the sleeve, which has a taper, has moved from its place, an annular gap is formed around it, it no longer touches the walls of the chamber and nothing prevents its further extraction.
AK and SVD also have such a process. But it happens in a completely different way. How? On the one hand, straying is spoken of as almost a key function that ensures the reliability of the Kalashnikov assault rifle, on the other hand, this is not written about in the NSD or in any other literature. But there are a lot of conjectures of home-grown "gunsmiths" on weapon forums, discovering mythical angles, worm gears and other jacks in the AK locking scheme.
Here's the thing. First, from a purely engineering point of view, the task is not easy - to reduce the complex manual movement in two planes to one longitudinal movement of the bolt carrier. In addition, it is necessary to solve a number of problems that have nothing to do with straining. I already talked about one of them when I showed how the problem of jamming when rolling was solved and which remained unresolved in AR.
Secondly, the solution lies in an area that is accessible only to top-class engineers, to whom, of course, Mikhail Timofeevich Kalashnikov belonged. This is the realm of mental 3D modeling. This feature of the constructor was noted by one of his colleagues, unfortunately, I do not remember who.
In order for the starting to work, in the locking unit there must be somewhere the same angle between the two parts, which ensures the longitudinal shift of the sleeve with the shutter to its turn. There are no such angles on the shutter. As for the corners in the cutouts and on the combat stops, which meticulous and inquisitive people find in the drawings of the shutter or liner, I can reassure you, they have nothing to do with starting. These are technological angles for sampling the inevitable error in production when mating surfaces, due to the type of tool or simply to facilitate their disengagement. A common thing in mechanical engineering. Let's see how the details of the mechanism interact.
So, when rolling, the bolt carrier (ZR) pushes the bolt forward with the transverse platform 1.1, resting on the edge 2.1 of its leading protrusion. After the left combat stop with the chamfer 2.4 hits the bevel in the insert 3.1, the shutter will turn and its leading protrusion with the edge 2.2 will fall on the locking edge of the figured groove 1.2 ЗР. After the shutter is completely locked, the leading protrusion falls into the free-wheeling pocket of the ZR.
When unlocking, after sampling the free stroke, the leading protrusion of the bolt with its facet 2.3 slides along the unlocking face of the figured groove 1.3 ЗР, turning the bolt until its lugs with cutouts in the liner are completely disengaged. Disengagement follows the same principle of separating any two parts. Technological angles, laid down for sampling inevitable errors when connecting nodes, work to wedge them when disconnecting. What does this mean? When the shutter is turned, the unlocking force is spent not on the entire sliding path of the plane of the stops on the combat edges, but only at the very beginning. Actually, the ZR spends its energy on unlocking only at the moment of wedging of the stops, then only the friction of the sleeve bottom against the shutter mirror interferes.
After disengagement, the left combat stop with its chamfer 2.4 falls on the same bevel 3.1 of the insert, which threw it in the reel to disengage from the transverse platform ZR. After disengaging the lugs, the leading protrusion continues sliding along the figured groove at section 1.4. The bolt with its chamfer begins to press on the bevel, the angle of which is 35 degrees, which, in theory, should prevent the shutter from turning normally (!).
Now we carefully look at the photo and do a thought experiment: we unfold the left combat stop together with the bevel on the liner counterclockwise from the viewer's side, bringing it closer to the leading ledge. And here it is, the coveted corner formed by the bevel on the insert 3.1 and the unlocking edge 2.3.
In the diagram, for ease of understanding of the process, I have brought the leading protrusion and the left stop into one shape. As you can see, the stroke length of the bolt carrier Szr is approximately twice the stroke of the bolt Sz and, accordingly, the effort to extract the sleeve (in fact, moving away) is twice as large.
That's the whole secret of getting away. There is no multiple increase in the effort to extract the sleeve, but what is there is quite enough.
Let me emphasize that starting reliably works only on a tapered sleeve, in a scheme where unlocking occurs after the residual pressure in the chamber is released. Its use in Stoner's scheme is meaningless.
