AR-15 Barrels from a wide selection of barrels made by Wilson Arms,  E. R. Shaw, and JP Enterprise.  Most barrels are chambered and bored to 5.56 NATO, this is the standard for all because they will fire .223 cal. and 5.56 Military rounds.  All Barrels come with Barrel Extension, alignment pin, gas port hole drilled, Front sight tower installed,  Barrel nut, and head spaced unless noted as a stripped barrel.