The Bushmaster ACR redefines the term "modular" with the extraordinary ability to change calibers, barrel lengths, and stock configurations in minutes-without the use of tools. A quick-change barrel system teams with a multi-caliber bolt carrier assembly allows you to quickly change to a 10.5", 14.5", 16.5" or 18" barrel in .223/5.56 or 6.8 Remington SPC. The ACR comes standard with a 16.5" cold-hammer-forged barrel that has an innovative coating to enhance longevity and a birdcage-style hider to control muzzle flash. ACRs have an adjustable, two-position, gas-piston-driven operating system supported by hardened internal bearing rails. Each has a free-floating, military-standard, 1913 monolithic top rail for mounting optics, fully ambidextrous controls, and a high-impact composite lower receiver with a textured magazine well and modular grip storage. The Basic Folder model has a folding, six-position telescoping, high-impact polymer stock with a rubber butt pad and sling mount. All ACRs have Magpul MBUS front and rear flip-up sights and come in an oversized hard case with a 30-round magazine.