Rook Armory is proud to announce that we have added two rifle rounds to our product line.  223 Remington and .300 AAC Blackout currently only available in NEW BRASS!  Sold in 500 round gently used military surplus ammo cans or 250 round cartons.


I have received a lot of questions regarding the difference between 0.223 Remington and 5.56X45mm NATO.  To help explain, first some brief history from Wikipedia…


In 1957 research into the development of a military 0.22 caliber rifle created the Remington 0.222 Special.  Due to there being several 0.222 caliber cartridges under development, the 0.222 Special was renamed to 0.223 Remington.  The cartridge became the standard for the US Army in 1962.  In 1972 Fabrique Nationale (FN) created a new class of ammunition for NATO.  It was based on the 0.223 Remington cartridge used by the US Army, but with greater range and effectiveness.


While the 0.223 Remington and 5.56X45mm NATO chambers have slightly different dimensions, the cartridges themselves are identical in dimension.  The cartridge dimensions are often confused with the difference in chamber dimensions.  As a result, it is a common misconception that the cartridges have different dimensions.  However, the cartridges are loaded to different pressure levels, the 5.56X45mm NATO being greater.  The 5.56X45mm NATO chamber dimensions offset the higher pressure of the cartridge with a longer throat, which often confuses some into thinking that the cartridge itself is longer.  Having said all that, supposedly 0.223 Remington can be fired safely from firearms chambered for 5.56X45mm NATO.  Barrels chambered only for 0.223 Remington are not designed to handle the 5.56X45mm NATO pressure.


Now having said that, a 0.223 Wylde chamber is used on 0.223 caliber rifle barrels to allow them to safely fire either 0.223 Remington or 5.56X45mm NATO ammunition.  Bill Wylde of Greenup, Illinois compared the two cartridges and changed the chamber of the barrel.  This chamber specification is referred to as 0.223 Wylde or 0.22 Wylde.  The chamber is made with the external dimensions and lead angle as found in the military 5.56X45mm NATO cartridge.  Furthermore, it possesses the 0.224 inch free bore diameter found in the civilian SAAMI 0.223 Remington cartridge.  Wylde’s hybrid chamber was designed to exploit the accuracy advantages of the 0.223 Remington chamber without problems concerning over-pressure.  This also prevents compromising the functional reliability of semi-auto firearms, like the AR-15 family, when using 5.56X45mm NATO military ammunition.

Remember to always check your firearm specifications to ensure you are using the intended ammunition for your firearm.  Serious injury or even death could result from not using the ammunition your firearm was designed to handle.


Want to know more about your favorite rounds?  Take a look at the SAAMI website for all the information you could ever want regarding dimensions, etc…


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