Heckler & Koch G36 & Operating Mechanism with full details
https://specialmilitaryforces.blogspot.com/2017/11/heckler-koch-g36-operating-mechanism.html
Operating Mechanism :- The G36 uses a short-stroke piston system from which HK later developed the HK-416's impingement system. Unlike direct impingement, this system takes gas trailing the bullet to operate a piston instead of pushing directly on the bolt. The G36's bolt is operated by a cam that guides the bolt carrier by its respective cutout. Then when fully pushed forward 7 radial locking lugs fully enclose the chamber.
HK included several design features that are essential in modern military firearms. For example, the bolt locks back after the last round is spent (this can be deactivated), and at the front end of the trigger guard there is a bolt catch button. The cocking handle can be switched from either end, folds in, and unfolds from a spring so the shooter need not unfold it by hand before firing. Another feature of it is that it doubles as the forward assist, which is used in the instance that the spent cartridge ejected but the next one did not properly extract and go into battery. In addition, the ejection port has a brass deflector to mitigate the amount of casings that may strike the face of left-handed operators. Instead of a dust cover which has the need to be flipped back up when the gun isn't in use, the bolt acts as the seal from dirt.