The difference between the 223 Remington and 5.56mm NATO chambers is in the throat area ....

The throat in a 223 Remington chamber is typically .085" while the throat in the 5.56mm chamber is typically .162"...

The added space in the 5.56mm chamber compensates for the added pressure inherent in the 5.56mm NATO round...

Tanner already schooled you on the AI case...

Now post a pic of you and your 223AI...