Both the 5.56 NATO and the .223 Remington have diameters of .224 inches and their external cases make them interchangeable size wise for multiple firearms, and they both hit the market in the 1950’s. But that’s where the similarities end.
The chamber pressure varies substantially between the the 5.56 NATO and the .223 Remington with the 5.56 at 58,000 PSI and the .223 at 55,000 PSI making it safer to fire the .223 from firearms designed for the NATO 5.56, but not the other way around. The 5.56 NATO requires a longer chamber throat which is one of the reasons why it may not be able to fire from rifles that can handle a .223 Remington. Depending on the manufacturer, the NATO may also have thicker walls giving it the ability to withstand higher pressures compared to a .223.
How the 5.56 NATO and .223 Remington Match Up
5.56 NATO | .223 Remington | |
Length | 2.26” | 2.26” |
Primer | Centerfire | Centerfire |
PSI | 58,000 | 55,000 |
Twist rate | Fast | Slow |
Manufacturing guidelines | NATO | SAAMI |
Throat | .125” longer than .223 Remington | .125” shorter than 5.56 NATO |
Cost on average | $0.43 – $0.53 per round | $0.42 – $0.50 per round |
For sports and hunting at medium and close range, you’re going to want the .223 Remington over the NATO 5.56 as the slower twist may help with accuracy for the lighter cartridge as it will be less likely to overstabilize. When long range does matter in tactical situations, the NATO 5.56 is heavier and can keep a more accurate trajectory with the faster twist than the .223 Remmington. This is one of the reasons why the 5.56 it is preferred over the .223 by militaries and for tactical use.
The 5.56 NATO was invented by Eugene Stoner in the 1950’s, and yes, it is the same Eugene Stoner from Armalite who owns the patent for the gas operated bolt and carrier system and AR-10. This same system eventually led to the M16, and Eugene is the creator of the AR-15. The .223 was introduced by Remington in the 1950’s and intended for use in the AR-15 and tactical rifles. If you’re out hunting white tail or practicing for a competition, you’re going to want the .223 over the 5.56 as it tends to be less expensive, can give more accuracy at shorter ranges, and you don’t need as big of a punch for most food based hunting like deer and boar.
And those are the differences between the .223 Remington and 5.56 NATO.