A recent gun show discussion revolved around Direct Impingement (AR platform) versus Piston Gas Operating System performance and the benefits of both. Although both systems are outstanding and proven in every environment everyone agreed that the short-stroke gas operating system incorporates the benefits of both. Most beneficial is the short stroke system's cleanliness and it's ability to limit recoil based on the system's lower reciprocating weight because the piston and rod are disconnected from the bolt group (see pictures below). Full stroke operating systems that have the piston connected to the bolt group have greater weight that is needed to be slowed during recoil and reset. Pictured below is the Bushmaster ACR's short stroke gas operating system reflecting the operating rod and bolt carrier being two separate pieces. If you're in the market to upgrade your AR, there are many kits available to convert a AR direct impingement gas system to a short stroke platform.
Pictured below is the Bushmaster ACR Enhanced we fired at the range. The pictures show the ACR with the stock both extended/collapsed with an AAC M4 2000 suppressor mounted. The ACR's modular design allows the user to easily change the system's stock, barrel, and hand guard by only manipulating a pin or a lever. The ACR's ambidextrous magazine release, bolt catch/release, fire selector and non-reciprocating charging handle make this weapon system truly adaptable for any user. Although the ACR's cost may price some out of the market, the ACR is still a less expensive option when building a comparable piston AR platform. If you can, buy the ACR you will not regret it!