The automatic pistol is a weapon skin for ZDoom (not the original Doom) and it is also the difference between the original pistol and the automatic pistol.
1. Go to your source-port (for Doom, eg. GZDoom) directory
2. Place the AutoPistol.pk3 file to any engine what you have.
3. Type IDKFA (not from the console!) and enjoy.
1.0 - Initial release