We have paired our “MULTI-ACK” Multi Caliber Upper Receiver, with this highly accurate Windham Weaponry barrel assembly. The barrel assembly measures 16” in length and is turned in a heavy profile. The assembly comes complete with the Barrel Extension, WW Free Float Handguard Barrel Nut, an installed Low-Profile Gas block and Gas Tube, and A2 Birdcage Flash Hider.  The rifling is 1 turn in 24 inches – right hand twist – with 6 lands.  Machined from 4150 Chrome Moly Vanadium 11595E Steel, this quality barrel is Chrome Lined in both the Bore and Chamber for prolonged wear resistance and ease of cleaning. Additionally, the Black Manganese finish on this barrel assembly offers protection against rust and corrosion. This assembly also includes the complete 450 Bushmaster Bolt and 5 round 450 Bushmaster magazine. Upper receiver is included.  All top-quality Windham Weaponry parts – made in the USA.