The AR-10A4 Complete Upper Assembly features a double lapped, chrome lined barrel. The Picatinny Rail on the upper receiver and the gas block allow rapid and repeatable interchange of removable iron or scope sights.
Each ArmaLite Complete Upper Assembly includes a forged upper receiver assembly, barrel assembly, bolt carrier group and charging handle assembly. All complete upper assemblies are test fired as complete rifles before shipping.
AR-10 uppers use 7075-T6 aluminum.
.750 at the journal (under the gas block)
Model: AR-10 A4 Complete Upper Assembly with Green Handguard
Caliber: .308/7.62 X 51mm NATO
Barrel: 20" Double Lapped, Chrome Lined, 4140 steel, M-4 Feed Ramps
Rifling Twist: RH 1:11.25"
Muzzle Device: Flash Suppressor, Threading: 5/8"-24
Front Sight Base: Picatinny Rail Gas Block. Top of gas block is .398 (+/- .010) lower than top of receiver
Upper Receiver: Forged Flattop with Picatinny Rail 7075-T6 Aluminum
Finish: Hard Anodized Aluminum, Manganese Phosphated Steel