[RPKESQ]

Let's start with basics. There is only gas. Both systems use gas as the generator of the motive force to cycle the weapon. They are different as to how the use the gas only by slight degrees.

In a (Stoner) AR-15 system as designed the gas flows from the gas aperture to a tube that leads back to the piston which is integral with the bolt. Gas pushes the piston, piston transfers that energy to the bolt which moves back and utilizing cam surfaces rotates the locking portion of the bolt which unlocks and continues back into full recoil (which then the recoil spring after being compressed, releases its stored energy and forces the bolt back into battery (locked)).

Positive attributes of this system is lighter weight and less machining of some parts or reduction of parts count (which are cheaper to produce).

Negative attributes are greater chamber/bolt area fouling, sensitivity to powder type and cleaning and the requirements for a recoil spring and housing protrusion in the rear of the action.

In an M-1, M-14, FN FAL, AK , Mini-14 type system the gas is bled off into a gas cylinder that is attached to the barrel. A "piston" which may be a separate part or just a machined end of the operating rod (or piston rod) is pushed back by the gas, which causes the operating rod to transfer the backward motion to the bolt which in turn moves backward on some cam surfaces which cause the bolt head to rotate and unlock the bolt, causing it to continue backwards until the recoil spring is compressed which then drives the bolt forward into battery.

Positive attributes of this system are reduced chamber fouling, low sensitivity to powder types and cleanliness, no recoil spring requirement for a behind the action recoil spring and housing, which enables a folding (or no) stock. Also large robust parts for durability.

Negative attributes are higher manufacturing cost and heavier weight.


If you can use the proper powder type and keep the weapon clean the Stoner system is reliable and lighter.

If a more expensive, heavier weapon with greater parts durability and greater reliability in poor conditions is required then the M-1, M-14, AK, system is desirable.

Military accuracy is totally independent from gas system type with proper construction. In a civilian world of competition, it is easier to build an accurate system with the Stoner gas system.