Windham Multi-Caliber System Upper Receiver Kit 5.56mm to .300 Blackout

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. Barrels are chrome lines and machined from 4150 chrome moly vanadium steel, finished in black manganese phosphate. Upper receivers are CNC machined from foreged 7075 T6 aircraft aluminum and finished in hardcoat black anodize. Bolts are machined from Carpenter 158 steel. Includes .223/5.56mm M4 barrel assembly, integral railed forend and a .300 Blackout barrel assembly with railed gas block and A2 flash hider. Change is allowed using the same bolt/bolt carrier and magazines.