FN America Ar-15 Button Rifled Barrel Oal M4 . 56 Carbine. Suitable for most M4-pattern rifles these Rifle Barrels by FN America feature M4-style feed ramps and a barrel extension that promote consistent feeding. The bore and chamber of the FN America AR15 Barrel are chrome-lined to resist corrosion and greatly improve the barrel's life and reliable chambering/extraction. Fn America also resists external corrosion and oxidation for a long service life. Add an FN America AR15 Replacement Barrel to your existing rifle to completely transform your shooting game. Package Contents: FN America Ar15 Barrel 16inch Bb M4 5.56 Carbine The FN America Ar15 Barrel 16inch Bb M4 5.56 Carbine is a quality addition to the FN America lineup. For more great deals on AR15 Barrels by FN America please browse our FNH USA Gun Parts page.