What is the difference between 222 and 223 calibre rifle cartridges ? – Hobbies & CollectiblesReport
The .222 Remington was the parent case for the 5.56×45/.223 Remington cartridge, and it was also the parent case of the .222 Remington Magnum (which was rejected by the military prior to the adoption of the 5.56×45). The .223 has a longer casing, which holds more powder, as well as differences in neck and shoulder measurements. The two cartridges are NOT interchangeable.