Unless you live in NC....
Each person can not define their own threshold -- the law does and the law states shooting through locked doors = bad.
Here, we can use deadly force to prevent a forcible entry to our home if we are in fear of serious bodily harm or sexua assault, or have reason to believe the intruder is about to commit a felony.
NC GENERAL STATUTE 14â€‘51.1. Use of deadly physical force against an intruder. (This is commonly called the "Castle Doctrine.")Now, I'll admit, that I would probably let an unknown intruder kick the door in before I'd pull the trigger. My house is laid out like a maze, and there is a lot of good cover between the entryway and the rest of the house (especially if I'm upstairs). A BG would have to be moving pretty fast and know the layout of my house to have any sort of advantage once inside, especially if it's night-time.
(a)A lawful occupant within a home or other place of residence is justified in using any degree of force that the occupant reasonably believes is necessary, including deadly force, against an intruder to prevent a forcible entry into the home or residence or to terminate the intruder's unlawful entry (i) if the occupant reasonably apprehends that the intruder may kill or inflict serious bodily harm to the occupant or others in the home or residence, or (ii) if the occupant reasonably believes that the intruder intends to commit a felony in the home or residence.
(b)A lawful occupant within a home or other place of residence does not have a duty to retreat from an intruder in the circumstances described in this section.
Plus, a busted-in door frame makes for a much more "easy to explain situation" when the LEO's show up to "collect" the BGs...