RG 5.56mm 62gr FMJ Ammunition

RG 5.56mm 62gr FMJ Ammunition

RG 5.56mm 62gr FMJ Ammunition.

Note: There are two primary differences between the .223 Remington and the 5.56 NATO. The first is that the 5.56 is loaded at higher pressures than the .223. The 5.56 NATO cartridge runs around 58,000 pounds-per-square-inch (psi), while the .223 Remington is loaded to approximately 55,000 psi.

While this isn’t a terribly significant difference, that pressure difference can create a problem when you take into account the fact that the 5.56 chamber is not identical to the .223. The leade–the portion of the chamber in front of the cartridge case–in a 5.56 rifle is 0.125” longer than the .223 Remington. This means that firing a 5.56 NATO cartridge in a .223-chambered weapon will increase pressure to 65,000 psi or more.

This is why the Sporting Arms and Ammunition Manufacturer’s Institute (SAAMI) warns against shooting a 5.56 NATO cartridge in a rifle chambered in .223 Remington. “This can result in serious injury or death to the user and/or bystanders, as well as damage to the firearm,” the organization writes.

Frank C. Barnes adds in “Cartridges of the World” that while a bolt-action rifle chambered in .223 Remington will likely be able to fire a 5.56 NATO cartridge, the same can’t be said for semi-auto guns.