FN America. 56x45mm. Made In The M16 Styling Constructed Of A Mil-spec Steel And Finished In Black Manganese Phosphate This 16 Button Rifled Fn America Barrel Is A Great Choice For Any Carbine Length Ar-15 Rifle. Chambered In .223 Rem / 5.56x45mm The Chrome Lined Chamber With Its Feed Ramp Will Provide More Consistent And Reliable Feeding While Shooting. Package Contents: FN America The FN America 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.