Enter Von Croy's apartment, go to where the Rig 9 handgun is. do not pick up the gun first, that brings the cleaner. instead, go to the ammo clip right next to the column (where the dining room table is). I found that if you pick up this magazine first, it wont dissapear until you pick up the handgun. I picked up 60 magazines, and could have done many more. As soon as I got the gun, when I went back and picked up that clip, it then dissapeared.
Unlock hidden trailer
Finish the game with all the secrets to unlock the trailer.
Run off the end of a ledge and tap the square button. Lara will do a forward somersault and hit the ground running in the original direction.
Tap action until she does two punches, then hold forward, and press down on the action button, hold it for 1/2 second. Keep doing this until she does 3 kicks.
To snap a baddies neck go into stealth mode. When you are right behind them hold down action.