The short-stroke gas piston require less maintenance and cleaning.
The Slostin machine gun uses a similar operation but with gas pistons on each barrels.
The gas piston pushes the bolt carrier rearward, where it is returned to the forward and locked position by a spring.
The gas piston is vertical behind the pistol grip.
Its action was powered by a short-stroke gas piston.
It is unusual that the top barrel acts as a gas piston.
The AR-18's action was powered by a short-stroke gas piston above the barrel.
Rounds had struck the gas piston and upper handguard, making it impossible to open the bolt.
The single mainspring is located on top, between the two gas pistons.
The gas piston itself has an effective range of about twenty feet.