A bullet fired from a gun is not released. It is released out with the subsequent shot. It is known as:
Tandem or piggyback bullets are ejected one after the other, when the first bullet having been stuck in the barrel fails to leave the barrel and is ejected by the subsequently fired bullet Ref: Parikh, 6th ed, page 4.26.
Dum Dum bullet
Tandem bullet
Ricochet bullet
None of the above