5.56 / .223
The AR-15's cartridge — 5.56 NATO and .223 Remington for defense, range, and varmint.
About 5.56 / .223
5.56×45mm NATO (and its close civilian cousin, .223 Remington) is the cartridge of the AR-15 and the most common centerfire rifle round in America. It's a light, fast, flat-shooting cartridge with mild recoil, which makes the AR-15 easy for almost anyone to shoot accurately — a big reason it's so popular for home defense, training, and recreational shooting.
A practical note on safety: rifles chambered in .223 Rem can't always safely fire 5.56 (which runs higher pressure), though 5.56-chambered rifles handle both. 5.56 is excellent for defense and varmint hunting, but check your state's rules before using it on larger game, as many require a bigger caliber for deer.
