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Operations of an assault rifle are based on utilization of propellant combustion gases diverted from the barrel bore into gas cylinder. To significantly enhance accuracy of fire the assault rifle uses the blow back shifted pulse (BBSP). The BBSP by nature is a delay of the shock of the firing unit in its rear position in relation to the moment the bullet escapes from the barrel, i.e. while the burst of the first two rounds are being fired at the rate of 1,800 rpm both the barrel and the firing unit are travelling along the guiding rail in the integrated carrier-stock toward its rear. The time before the firing unit compresses the buffer spring inside the carrier-stock above the foregrip and completes recoil cycle is enough for two bullets to escape from the barrel. The operator feels the recoil as a single aggregated shock which does not effect the trajectory of bullets already headed down range and, hence, allows a better hit probability. In the process of firing, two simultaneous actions are in progress: travel of the integrated firing unit inside the carrier-stock and movement of components of the firing mechanism.
A. Variable automatic fire.
To shoot in a full-auto mode, the operator should place safety shift into position "O" (ogon’ means fire in Russian), while the selector should be located in the "AB" position ( "AB" stands for avtomaticheskiy - automatic). The selector in this position shifts a trigger plate in such a manner that the disconnector comes into contact with one of the shoulders of the trigger plate. The operator pulls the extending side handle of the bolt carrier to bring it into rear position. At this moment the preliminary feeding of a round from the magazine by a special mechanism takes place. This operation takes place every time the bolt carrier travels to the rear. The bolt carrier pushes the hammer into its firing position while the sear holds it. Released and driven forward by both a return spring and the shock absorber, the bolt rams the round into chamber, and locks the barrel by entering its two locking lugs into recesses in the barrel extension. By pulling the trigger, its side lug presses upon the trigger plate. The latter turns around its axis to activate the sear. The sear also turns to release the hammer. The hammer, driven by the main spring, slides into its front position and hits upon the firing pin. The first round is fired.
Driven by blowback, the firing unit slides inside the integrated carrier-stock and compresses the buffer spring. As soon as the bullet passes the gas port in the barrel, a portion of gases escapes through the port into gas cylinder, activates the piston and, through the bolt carrier extension, pushes the bolt carrier with hammer rearward. The bolt turns to open the chamber. The empty case is extracted and ejected. When the bolt carrier and the hammer reach their rear position, the return spring, assisted by the shock absorber, pushes them forward. The sear being temporarily deactivated, the second cycle is initiated. The hammer in the high-rate mode, free from the sear, keeps on moving and decreases the time between shots.