Colt's ARs are experiencing an evolution of design adjustments due to the growing popularity of the 3-Gun competition. The competition models are the CRX, CRP, CRE, and CRL line of rifles, which are all hand-built in the US with 100% US-made components. These rifles have an accuracy guarantee of 1 MOA (three shots at 100 yards) when used with match-grade ammunition. Models include free-floating, 16–, 18–, or 20–inch match-grade barrels manufactured of 416 stainless steel and use .223 Wylde Match chambers for assured operation. They also have original direct-impingement action systems, extended tactical latch charging handles, two- or three-port Colt muzzle brakes, Geissele two-stage match triggers, and direct-impingement action systems. Most of them also employ a Magpul adjustable stock. The entry-level range from Colt Competitions, the CRX series, features non-adjustable low-profile gas blocks and is chambered in .223 Remington. An adjustable 4-position carbine-style stock comes with the CRX-16. An extended Colt Competition charging handle is a feature of the Colt "Expert" Model CRE-18 series. The Colt "Pro" Model CRP-16 and CRP-18 rifles include low-profile finger-adjustable gas blocks and a 16- or 18-inch barrel chambered for .223 Rem. The Colt "Pro" Model CRL-16 and CRL-20, chambered in.308 Win, provide an improvement in performance and power. The MOE pistol grip is included on the 20-inch model. To ensure optimal accuracy, the barrels are air-gaged. The CSR is a stripped-down version of the CRX.