5.56 NATO vs .223 Remington: Are They the Same?

Set a 5.56 NATO round next to a .223 Remington round and you’ll have a hard time telling them apart. The outside dimensions are nearly identical, and both are common in AR-15 rifles. But they are not quite the same cartridge, and the difference matters for safety.

The short answer

• .223 Remington is generally safe to fire in a rifle chambered for 5.56 NATO.
• 5.56 NATO is not recommended in a rifle chambered only for .223 Remington.
• Rifles marked .223 Wylde are designed to handle both.

Why the difference?

5.56 NATO is typically loaded to higher pressure than .223 Remington. Rifles chambered for 5.56 also tend to have a slightly longer throat (the leade, the space just ahead of the case where the bullet starts into the rifling), which gives that extra pressure room to settle. Fire a 5.56 load in a tighter .223-only chamber and pressure can climb higher than the rifle was designed for.

How to check your rifle

Look at the barrel. Most AR barrels are stamped near the muzzle or under the handguard with the chambering: “5.56 NATO”, “.223 Rem”, “.223 Wylde” or “5.56/.223”. When in doubt, check with the manufacturer before shooting 5.56 ammo.

What about accuracy?

.223 Remington fired from a 5.56 chamber can be a touch less accurate in some rifles because of that longer throat, though for most range work you won’t notice. For zeroing, drills and steel, a 55 grain FMJ load in either flavor does the job.

Our 5.56 load

Our 5.56 NATO 55gr FMJ, 250 rounds is a standard 55 grain load for AR-15s chambered in 5.56 NATO or .223 Wylde. Always confirm your barrel marking first.