For those builders who already have barrel parts, we offer this M4 Profile Crowned Barrel Sub-Assembly. The highly accurate 4150 Chrome Moly Vanadium steel barrel is chrome lined and rifled 1 x 9″ Right Hand twist. The muzzle is finished with a plain crown to comply with legal restrictions in States where threaded muzzles and flash hiders are prohibited – the bayonet lug has been machined off the A2 Standard Sight Base. The Assembly includes Barrel, Barrel Extension with M4 Feed Ramps, Barrel Nut, Front Handguard Cap, A2 Standard Sight Base with Square Post & Sling Swivel. Top quality Windham Weaponry parts – all made in the USA.