A rifle that works automatically and operates on gas is typically referred to as AR 15. ar15 is light weighted and has a magazine storage attached to the firearm. It was given this design keeping in mind that synthetic materials and aluminum alloys were to be used to build the rifle. It is mostly an automatic version of M-16 firearm present in the military arms of USA. This rifle was introduced to the world in the year 1963. Some famous versions of the ar 15 rifle are AR 15A2, AR 15A4, AR 15A3 and many more.
Presently AR-15 is used as the trademark for all semi-automatic rifles manufactured by the company that designs these rifles. These are the rifles which are sold to the law-enforcement bodies and similar customers. The mechanism used in AR-15 is the cycling mechanism. The bolt does the work of a piston and the work of the piston is done by the bolt carrier. This mechanism is totally different from prior gas systems. Using conventional mechanism was not initially considered by its designer but later it was with help of this that AR 15 was described. When the bullet passes the gas port on top of the front look base ok the rifle gas is knocked out of the barrel. The gas then enters the port and expands and is filled in the bolt carrier. Once locked the gas pushes the bolt back a bit. The bolt then forces it to get ejected from the port of ejection. There is a buffer made of plastic in behind the bolt carrier in the same level as the return spring. This spring then forces the bolt carrier to move to the chamber for the bolt but only after getting compressed. Then there is a twist that locks the bolt in the barrel extension.