A flat loop revolving firearm assembly can have a trigger mechanism configured to move a loop advance lever disposed between the trigger mechanism and a flat loop, and a hammer retractor lever disposed between the trigger mechanism and at least one hammer retractor bar. The hammer retractor bar can be configured to slide and contact a hammer thereby rotating the hammer to a cocked position and releasing the hammer to fire a cartridge removably disposed in a firing position chamber. The flat loop can have a plurality of flat loop links configured to revolve in parallel tracks into a firing position in response to motion imposed by the loop advance lever.

An automatic circulation shooting mechanism includes a gun body assembly, a gun barrel assembly, a bolt assembly, a recoil spring assembly, a triggering assembly, and a cartridge feeding assembly. Regarding the gun body assembly, a barrel fixing cap can separate from a barrel frame, so the gun barrel assembly mounted in the barrel frame can be replaced. The gun barrel assembly includes two barrel spring fixing seats disposed on a barrel, a barrel spring therebetween and a barrel extension. The barrel extension and a breech bolt of the bolt assembly are engaged for locking while shooting to allow the barrel and the breech bolt to recoil together by a linear freedom motion and affect the barrel spring, a bolt spring of the bolt assembly, and the recoil spring assembly for absorbing, storing, and releasing energy, thereby buffering recoil force of the shooting efficiently and attaining an automatic circulation shooting effect.

A gun includes a kinetic delay to reduce total recoil energy transferred to a shooter and extend the time of the recoil impulse to reduce felt recoil and increase controllability. In one embodiment, a bolt of a gun is longitudinally separated from a bolt carrier of the gun such that there is a delay between firing the gun and the bolt longitudinally impacting the bolt carrier. In one embodiment, the barrel is longitudinally separated from the bolt carrier such that the barrel longitudinally impacts the bolt carrier before the barrel longitudinally impacts a barrel stop of the gun when the gun is fired. In one embodiment, a locking bolt includes a bolt pin extending through a bolt pin slot in the bolt carrier and the bolt pin slot is elongated such that the bolt pin does not contact either end of the bolt pin slot when the gun is cycled.