Elvis...'Mitri...our resident brainiac
...as usual comes through with the perfect explanation of the differences between the two rounds....223 Rem and 5.56 mm NATO. The only thing he didn't mention is that the primers are crimped in on the military rounds.
The reason your primer pockets may appear to be loose is because when the crimp was removed a "heavy hand" may have been "involved".
We have used both military and civilian cases in a mate's Howa .223 and have noticed only minor differences in "fall of shot". Military cases are designed for a single firing then either discarded on the battle field or returned to the factory to be melted down and remade into new cases...which is why we always had to collect the spent rounds and account for at least 85% by weight after a range practice.