.223 .556

The .223 Remington (.223 Rem) is a rifle cartridge. The name is commonly pronounced either two-twenty-three or two-two-three Remington. It is commercially loaded with 0.224 inch (5.56 mm) diameter jacketed bullets, with weights ranging from 40 to 85 grains (2.6 to 5.8 g), though the most common loading by far is 55 grains (3.6 g). A 90 gr Sierra Matchking bullet is available for reloaders. The .223 Rem was first offered to the civilian sporting market in December 1963 in the Remington 760 rifle. In 1964 the .223 Rem cartridge was adopted for use in the Colt M16 rifle which became an alternate standard rifle of the U.S. Army. The military version of the cartridge uses a 55 gr full metal jacket boattail design and was designated M193. In 1980 NATO modified the .223 Remington into a new design which is designated 5.56×45mm NATO type SS109.

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