Windham Weaponry

Windham Weaponry's Multi-Caliber Upper Receiver Assembly Kit is designed as a unique upgrade for the AR15-type rifle, offering quick and easy caliber changes by simply switching out the barrel, and if necessary, the bolt/bolt carrier and magazine. Add the optic or iron sights of your choice, and this kit is "ready for the range." The barrel is chrome-lined and machined from 4150 chrome moly vanadium steel with a black manganese phosphate finish. The upper receiver is CNC machined from forged 7075 T6 aircraft aluminum with a hardcoat black anodize finish. The MCS 1 Kit includes a complete upper receiver assembly with .223/5.56mm caliber M4 barrel assembly; integral railed forend; (with barrel release levers, and barrel retaining block). Additionally, a .300 Blackout caliber barrel assembly is included allowing the change between .223/5.56mm caliber and .300 Blackout caliber by utilizing the same bolt/bolt carrier and .223 magazines. The .223/5.56mm bolt/bolt carrier and .223 magazines are utilized. The .300 Blackout caliber barrel assembly is complete with railed gas block, gas tube, and A2 flash hider.