When building an AR, there are multiple factors and tolerances to consider. When you are building an AR for 3-Gun competition, these factors change somewhat. The accuracy and reliability of the platform you’re building takes priority over many other factors. The ODIN Works 18″ Intermediate 3-Gun Profile SS Barrel comes from the factory with the popular .223 Wylde chamber, so both the .223 Remington and 5.56 NATO ammo can feed, fire, extract, and eject without a problem.