5.56 vs .223: What's the Difference Between These Popular Cartridges?

By Daniel Walker | April 19, 2024

Variances

Despite the striking similarities in external dimensions between the .223 Remington and 5.56x45mm NATO cartridges, a closer examination reveals some subtle yet significant distinctions. These cartridges have gained immense popularity since their introduction, finding widespread use across various applications.
 

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Despite their popularity, there remains a considerable amount of confusion and queries regarding the variances between these two cartridges. One of the primary questions often asked is whether 5.56 NATO and .223 Remington ammunition are interchangeable. 
 

Yes and no

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The answer is a mix of yes and no. In simple terms, .223 Remington ammunition can be safely fired from rifles designed for 5.56 NATO, but the reverse is not recommended—firing 5.56 NATO ammunition in a .223 chamber. This caution is warranted due to the higher chamber pressure generated by 5.56 NATO ammunition, combined with the slightly shorter throat in rifles chambered for .223.