223 vs 5.56: Complete Ammo Guide for AR-15 Owners 223 vs 5.56 is one of the most common ammo questions among AR-15 owners, rifle buyers, and new shooters. The .223 Remington and 5.56 NATO cartridges look very similar, but they are not always interchangeable. The short answer is simple: .223 Remington can generally be fired […]