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 Rifle
Caliber: .308/7.62 X 51mm NATO
Barrel: 20" 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: Gas Block with Picatinny Rail
Finish: Manganese Phosphated Steel