The M-15A4 Complete Upper Assembly features a double lapped, chrome lined\Chrome Moly Vanadium 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.
M-15 Uppers use 7075-T6 Aluminum.
.750 at the journal (under the gas block)
Model: M-15A4 Complete Upper Assembly with Green Handguard
Caliber: .223/5.56 X 45 mm NATO
Barrel: 20" Double Lapped, Chrome Lined\Chrome Moly Vanadium MIL-B-11595-E, M-4 Feed Ramps
Rifling Twist: RH 1:9"
Muzzle Device: Flash Suppressor, Threading:1/2" - 28
Front Sight Base: Gas Block with Picatinny Rail Top of gas block is .293 (+/-) lower than top of upper receiver
Upper Receiver: Forged Flattop with Picatinny Rail, 7075-T6 Aluminum
Finish: Hard Anodized Aluminum, Manganese Phosphated Steel