ArmaLite's barrels are custom-made for extreme accuracy and long life. This complete barrel assembly includes a Picatinny rail gas block, barrel nut, slip ring, slip ring spring, slip ring retaining ring, gas tube and handguard cap.
.750 at the journal (under the gas block)
Model: A4 Carbine
Caliber: .223/5.56 X 45 mm NATO
Barrel: 16" Chrome Lined\Chrome Moly Vanadium MIL-B-11595-E, M-4 Feed Ramps
Rifling Twist: RH 1:9"
Muzzle Device: Flash Suppressor
Front Sight Base: Gas Block with Picatinny Rail
Finish: Manganese Phosphated Steel