Once you pull the trigger and the firing pin makes contact with the round, the gun fires. It doesn't matter if what remains is ejected and a new round slides into place. In fact, it's supposed to work exactly like that.
It only lives in the TA until it is triggered, just like the bullet in the shell.
The problem is that the gun has been changed... The NIC is still in the chamber, but nobody can pull the trigger because that gun is no longer in use...