The .223 Remington

The .223 Remington One of America’s more accurate and easy-to-load for cartridges.

The .223 Remington appeared in 1964 as the civilian version of the 5.56mm NATO. The 5.56mm itself was essentially a compromise between the .222 Remington (1950) and .222 Remington Magnum (1958) for use in the US military’s new M16 rifle.

The cases of the .223 and 5.56 are essentially identical, but the chamber throat of 5.56 rifles is longer, and the pressures of military ammo are usually higher as well. Consequently it’s generally considered safe to fire commercial .223 ammo in 5.56mm chambers, but not the reverse. Also, 5.56 rifles generally have faster rifling twists, and some (though not all) military cases are heavier than commercial brass. Military primers also have heavier cups, to withstand higher pressure and the slam of automatic fire, especially in a hot rifle.


Until recently, the barrels on just about all commercial rifles had rifling twists of 1-turn-in-12″ (1:12″), the same as the original M16 adopted by the US military. This stabilizes lead-cored spitzers up to about 60 grains, and since most hunters used 40- to 55-grain bullets in the .223, the twist worked fine—and still does, when handloading conventional varmint bullets.

The military eventually increased bullet weights in some 5.56mm ammunition to increase effectiveness in various combat situations. In a few M16 variations the twist rate was changed to 1:7″, capable of stabilizing lead-cored spitzers up to 80+ grains in weight.

At the same time more American hunters wanted to use longer bullets, both for varmint shooting at longer ranges and for hunting smaller big game such as deer and feral pigs. Some longer bullets had conventional lead cores, while others were longer due to using “non-toxic” materials, for the entire bullet or just the cores.
By John Barsness

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