The butt
The knife at the end of a gun is called the bayonet.
Neither. It is called the muzzel
Breach
Threaded
It's called the Muzzle
It is called the "butt stock".
In the cartridge, which is placed at the back end of the barrel, in the chamber.
It's the very back end of a rifle or the bottom of the grip on a pistol.
It is the end of the stock as opposed to the end of the barrel end of the gun
Back of a boat is called stern and Bow is the front of a boat.
Firing pin is what strikes the back end of bullet igniting propellant
There is a part almost all guns called the extractor that, like its name implies, extracts the shell when the bolt of the gun recoils back.