Hey this relates perfectly to a question I have in reloading . Heres the short answer ;
1the NATO chamber is cut slightly different as above .
2 The NATO brass is thicker (it is after all military spec) with an identical load and bullet it will have higher pressures due to lesser case capacity .
3 the NATO necks are thicker and may stick in 223 chambers .

4 physically and demintionaly they are the same and are interchangable with the above considerations .