[Unclenick]

Yep. He may have said ".223 bullet" meaning a bullet for the .223 Remington (a .224" bullet). Some of the confusion is the cartridge nomenclature. The NATO version cartridge is called 5.56 mm, but that works out to .219" and refers only to the bore diameter drilled and reamed into a barrel blank before rifling it, so it does does not include the depth of the grooves between the rifling lands. A jacketed bullet is normally sized to groove diameter, not bore diameter.