The .223 Wylde hybrid chamber was designed by Bill Wylde of Greenup, IL to exploit the accuracy advantages of the .223 Remington commercial chambering without pressure problems or compromising the functional reliability when using the high velocity 5.56x45mm NATO military ammunition. Coincidentally, it shoots the relatively long and heavy grain bullets commonly used in the Sport Rifle Competition very well and is one of the preferred chambers for that use. This chamber is used by many rifle manufacturers who sell "National Match" configuration AR-15 rifles and upper receivers such as Performance Firearms. The .223 Wylde achieves better accuracy by having a chamber throat that is tighter than 5.56 NATO and it will still function reliably with both .223 and 5.56 ammunition. In short, it will give you the accuracy of a real SAAMI .223 Remington when using the good ammo, but will also allow you to use inexpensive 5.56 surplus ammo safely. It is truly the best of both .223 and 5.56 chambers.