.223 Remington is a sporting cartridge with almost the same external dimensions as the 5.56x45mm NATO military cartridge. It is loaded with a 0.224-inch (5.7 mm) diameter, jacketed bullet, with weights ranging from 40 up to 90 grains , though the most common loading by far is 55 grains.
The 55 Grain V-Max works darn good on those Rat Dogs in SD those Black Plague infested flea carrying varmints and people pick them up for pictures. While the tree huggers want to protect them, how many million do we need?
While the external case dimensions are very similar, the .223 Remington and 5.56x45mm NATO differ in both maximum pressure and chamber shape. The maximum pressures for some varieties of the 5.56 mm (different cartridge designations have different standards) exceed the SAAMI maximums for the .223 Remington, and the methods for measuring pressures differ between NATO and SAAMI. The 5.56 mm chamber specification has also changed over time since its adoption, as the current military loading NATO uses longer, heavier bullets than the original loading did. This has resulted in a lengthening of the throat in the 5.56 mm chamber.
Thus, while .223 Remington ammunition can be safely fired in a 5.56 mm chambered gun, firing 5.56 mm ammunition in a .223 Remington chamber may produce pressures in excess of even the 5.56 mm specifications due to the shorter throat.[/u]
So don't do it leave the cheap 5.56 ammo alone you may get away with it for awhile than KAAAA Boom ahhhh where is my hand, HELP!
.223 Barrel = .223 Ammo ONLY
5.56 Barrel = 5.56 or .223
