Certain AR-15 rifles utilize a short-stroke gas piston system rather than the traditional direct impingement system. In this design, expanding propellant gases drive a piston that cycles the action, instead of directly impacting the bolt carrier group. This operating mechanism often results in a cleaner, cooler-running rifle with potentially enhanced reliability and reduced wear. Examples include offerings from manufacturers like Adams Arms, PWS (Primary Weapons Systems), and Sig Sauer.
The potential advantages of this alternative operating system have led to its increasing popularity among enthusiasts and professionals. Favored for their purported reliability in adverse conditions and decreased maintenance requirements, these rifles offer a different shooting experience compared to direct impingement counterparts. This design, while more complex to manufacture, can offer improved accuracy and reduced recoil impulse due to a smoother operating cycle.
