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News Link • Self-Defense

.223 vs. 5.56: Which Ammunition is Safe for “My” AR-15?

•, by Dave Dolbee
The .223 Remington is a sporting cartridge with the same external dimensions as the 5.56x45mm NATO military cartridge. It is loaded with a .224-inch diameter jacketed bullet, with weights ranging from roughly 40 to 90 grains; the 55-grain being the most popular. Pressure is the primary difference separating the .223 Remington and 5.56x45mm. The .223s are loaded to lower pressures and velocities compared to 5.56mm. Due to its lower pressure, you can safely fire .223 Rem. ammunition in a 5.56mm chambered gun; however, the same cannot be said in reverse.
The 5.56x45mm ammo creates a higher pressure. This over-pressure will frequently cause difficult extraction, flowing brass or popped primers. In extreme cases, the over-pressure could damage or destroy the rifle and injure the operator. Chambers cut to .223 Remington specifications have a shorter leade (throat) area as well as slightly shorter headspace dimensions compared to 5.56mm “military” chamber specs. This contributes to the pressure issues.

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