.223 vs 5.56: the cartridges look identical, but 5.56 NATO is loaded to a different spec and its chamber has a longer leade. A rifle marked 5.56 NATO or .223 Wylde can fire both. A rifle marked .223 Remington only should stick to .223. This page carries both, from Winchester M193 and M855, PMC X-TAC and Fiocchi to Hornady, Federal, Frontier and Prvi Partizan.
Already know your chamber? Shop 223 Remington ammo or 5.56 NATO ammo.
What Is the Difference Between .223 and 5.56?
The .223 Remington is a commercial cartridge standardized by SAAMI, with a maximum average pressure of 55,000 psi. The 5.56x45mm NATO is the military version, standardized by NATO and tested with a different pressure method, so the published numbers aren’t directly comparable. In practice, 5.56 NATO loads run hotter, and the 5.56 chamber has a longer leade (throat) to handle them.
Chamber Safety: Which Ammo Is Safe in Your Rifle?
5.56 NATO chamber: fires 5.56 NATO and .223 Remington. .223 Wylde chamber: a hybrid made to fire both, common on match barrels. .223 Remington chamber: fire .223 only. Pushing 5.56 through the shorter .223 throat can raise pressure past SAAMI limits, which shows up as flattened primers or hard extraction. Check the marking on your barrel. When in doubt, follow your rifle maker’s guidance.
Which Should You Buy?
Range and bulk: Winchester M193 55 gr FMJ, PMC X-TAC and Fiocchi FMJBT for 5.56 rifles, or Federal American Eagle, Scorpio and Armscor 55 gr FMJ for any .223-safe rifle. Green tip: Winchester M855 and PMC X-TAC 62 gr LAP. Many indoor ranges ban steel-penetrator ammo, so check before you go. Match: 68–77 gr BTHP from Frontier, Hornady and Prvi Partizan. Heavier bullets need a faster twist, so check your barrel. Varmint: Hornady and Fiocchi V-MAX. See our full .223 vs 5.56 guide, our best 5.56 ammo guide and our ammo and magazine laws guide.
FAQ
Is .223 the same as 5.56?
Not quite. They share outside dimensions, but 5.56 NATO is loaded to a different spec and uses a chamber with a longer leade. A 5.56 rifle fires both. A .223-only rifle should stick to .223.
Can I shoot 5.56 in a .223 rifle?
It isn’t recommended. The shorter .223 throat can push 5.56 pressure past SAAMI limits. Use .223 Remington unless your barrel is marked 5.56 NATO or .223 Wylde.
Can I shoot .223 in a 5.56 rifle?
Yes. A 5.56 NATO or .223 Wylde chamber safely fires .223 Remington.
What is .223 Wylde?
A hybrid chamber designed to fire both .223 Remington and 5.56 NATO safely, common on match AR barrels.
Should I buy .223 or 5.56 for my AR-15?
Check the barrel marking. If it says 5.56 NATO or .223 Wylde, either works. Pick 5.56 M193 or M855 for bulk training and .223 for varmint and match loads. If it says .223 Remington, buy .223.