Enable the "Full ammunition" code after getting the weapon you want. Resume the game and press the fire button. As soon as you fire, press Start. After you resume the game again, the weapon should fire on its own as many times as desired, until you run out of ammunition. Press R1 again and sometimes it will switch to the secondary weapon. However, you cannot switch back to the first fired weapon. Note: This causes the game to slow down with a rocket launcher or Redeemer.