It is the Carbine (short rifle) version of the AR15. AR stands for Armalite Rifle. It is a semi auto rifle.
Gun is not an acronym, and does not stand for nor abbreviate any other word.
Gun rack
Get a manual.
Type your answer here... you squeeze the buttons on each side of it and slide it off.
Impossible to answer without knowing the type of gun.
Machine gun Kelly
No, It is a type of gun
I would find it difficult to find out what type of gun you have.
Classic Deluxe
The diameter of the bullets
Against
Pump