AB-5.45 and AB-7.62

 AB-5.45 and AB-7.62 are assault rifles, chambered with 5.45x39mm and 7.62x39mm rounds respectively. AVB is a battle rifle, chambered with 7.62x54R round, LCZ B20 is its 7.62x51 modification. Weapons automatics is based on a delayed blowback and rear sear, which is more typical for submachine guns, machine guns and automatic guns than assault rifles and automatic rifles. 

The shot is made when the shutter is open. Weapon automatics' moving parts before firing are in the rear position, and the cartridge is not in the unlocked chamber. After pressing the trigger, locking assembly begins to move forward under the pressure of the return spring, and reforwards the cartridge into the chamber. When an assembly comes to its most forward position, the locking lever locks the barrel and strikes at the shutter located in the skeleton of the drummer, that skewers the capsule holder. 

The shot is made. Bottom part of sleeve rests on having a cup of free lift shutter striker, which at this moment is not tightly coupled with the barrel. Striker with the sleeve is moved back and acts as the frame, which begins to move back and affects the skeleton of the shutter, and then on the locking lever, rests against a ledge receiver. The valve uncouples with the receiver, the sleeve extracts and the compression spring returns.