Colt® AR15-M4 LE6940 Piston Semi-automatic 5.56 NATO Rifle
Developed for the U.S. Army... now available for civilian use. The Colt® LE690 APC (advanced piston carbine) is a lightweight, highly accurate alternative to the traditional direct gas impingement system found in most ARs.
What's the advantage? Piston-driven systems run cooler and cleaner, and are therefore generally more reliable and have a longer life span than direct gas systems. That means more bang for your buck over the long haul. And a more reliable rifle, for when you need it most.