Finding a cheat in Black.

I found a cheat in the game Black. Yes, some of you may not want to read this, because this is a old game. BUT, on the last level on the story, when you see the terriost running across the street, kill him, and walk over to his body for unlimited ammo. This ONLY works for the difficulty you are playing on for this level. Example: You click on the last level, and it tells you what difficulty to play on. You choose hard, and you kill the terriost, walk to his body, and do whatever else to finish the level. Now, you play the level again, and choose Black Ops. You look at your ammo capacity, and you do not have unlimted ammo. So, it only works for the difficulty you finished the level.