5.56 NATO vs .223 Remington: what's the difference?
They look identical and fit the same magazines, but they're loaded to different standards. Here's what that means for which ammo your rifle can safely fire.
Put a 5.56 NATO cartridge next to a .223 Remington and you'll struggle to tell them apart. Both use the same external case dimensions, fit the same magazines and fire the same diameter bullet. The difference is in how they're loaded and in the chamber each one is meant for. That difference decides which ammo your rifle can safely shoot.
Same outside, different standards
.223 Remington is a commercial cartridge standardized by SAAMI (the Sporting Arms and Ammunition Manufacturers' Institute) in the U.S. 5.56x45mm NATO is the military cartridge, specified under NATO standards and, on the commercial side in Europe, C.I.P.
The external case dimensions are the same. What differs:
- Pressure. 5.56 NATO is generally loaded to a higher pressure than .223 Remington. Hornady puts the two at roughly 58,000 psi and 55,000 psi.
- How pressure is measured. SAAMI and NATO/C.I.P. measure pressure at different points on the case, using different equipment. SAAMI notes that numbers produced by different methods can't be converted into one another, so treat the published figures as "higher vs. lower" rather than an exact comparison.
- Case construction. Military-style brass is often thicker, which can leave slightly less room inside the case. This varies by maker, so don't assume it.
Why the chamber matters: throat and leade
The biggest practical difference is inside the rifle. The throat (or leade) is the short, unrifled section just ahead of the chamber, where the bullet travels before it meets the rifling.
- A 5.56 NATO chamber has a longer throat. Hornady describes it as about 0.125" longer than a .223 Remington throat.
- A .223 Remington chamber has a shorter throat.
Fire a 5.56 round in a short-throated .223 chamber and the bullet meets the rifling sooner. Pressure can then climb above what the rifle was designed to handle. Hornady says this can exceed 65,000 psi, which is why SAAMI lists that combination as unsafe.
Going the other way, a .223 round in the roomier 5.56 chamber simply has a little more space. That's why it's generally considered safe. The trade-offs are possible small accuracy differences and, in some short-barreled rifles, less reliable cycling with milder .223 loads.
What about .223 Wylde?
.223 Wylde is a chamber design, not a cartridge. It was created to fire both .223 Remington and 5.56 NATO safely while keeping good accuracy with .223. It isn't a SAAMI standard, so the manufacturer's word is what counts. Many AR-pattern barrels are sold in .223 Wylde. Check the marking and the manufacturer's documentation to confirm it's approved for both.
Which ammo can my rifle fire?
| Barrel marked | .223 Remington | 5.56 NATO |
|---|---|---|
| 5.56 NATO (military-spec chamber) | Generally yes | Yes |
| .223 Wylde | Yes, if the manufacturer approves | Yes, if the manufacturer approves |
| .223 Remington | Yes | Not recommended (SAAMI: unsafe combination) |
| Unmarked or unclear | Ask the manufacturer or a gunsmith first | Ask the manufacturer or a gunsmith first |
Some rifles made to commercial specs are sold as "5.56" but may not have a full military-spec chamber. That's another reason SAAMI tells owners to confirm with the manufacturer.
Shopping for 5.56 and .223 on Price Dope
Price Dope tracks the two calibers separately, so a listing appears under the caliber the retailer lists it as. If your rifle is chambered in 5.56 NATO or .223 Wylde and your manufacturer approves both cartridges, you can compare both tables. If it's marked .223 Remington only, stick to the .223 table.
Both tables below list in-stock offers first and rank them by cost per round. Every offer shows when it was last checked. Full listings, with filters for bullet weight, bullet type and case material, are on the 5.56 NATO and .223 Remington caliber pages. If you're new to comparing box sizes, see cost per round, explained.
Sources
- SAAMI, Frequently asked questions (5.56 and .223 safety; pressure measurement methods).
- Hornady, What is the difference between 5.56 NATO and .223 Rem ammunition?
- The Armory Life (Springfield Armory), What is .223 Wylde?
5.56 vs .223 FAQ
Can I shoot .223 Remington in a 5.56 NATO rifle?
Generally, yes. SAAMI says it is safe to fire .223 Remington in a rifle with a military-specification 5.56 chamber, and notes that some 5.56 chambers aren't built to that spec, so confirm with your rifle's manufacturer. Some short-barreled rifles may not cycle reliably with milder .223 loads.
Can I shoot 5.56 NATO in a rifle marked .223 Remington?
It isn't recommended. SAAMI lists 5.56 NATO in a .223 Remington chamber as an unsafe combination, because the .223 chamber's shorter throat can push pressure above what the rifle was designed for.
What is .223 Wylde?
A chamber design, not a cartridge. It was created to fire both .223 Remington and 5.56 NATO safely and accurately. It isn't a SAAMI standard, so check that your manufacturer approves both cartridges for that barrel.
How do I know what my rifle is chambered for?
Look at the barrel markings, which are usually stamped near the chamber or under the handguard on AR-pattern rifles, and check the owner's manual. If the markings are missing or unclear, ask the manufacturer or a qualified gunsmith before you fire anything.
Are 5.56 and .223 the same price?
It varies by listing, so compare them yourself. Price Dope tracks the two as separate calibers. The tables below rank current in-stock offers for each by cost per round.
Prices shown come from connected retailers' latest checks and change often. Price Dope doesn't sell anything and may earn a commission from retailer links. Disclosure · How we collect prices · Editorial standards
