1)put your rifle at the first place in your inventory.
 2)save game (remember how many ammo you have for your rifle,
 yellow one and bullets)
 3)edit your save game for example save3.10920$.(you need a hex editor)
 4)go to line 0000c760
 5) the right code for example 0B55A is the code of the rifle,
 the yellow are the bullets (0B08f and 0B07E).
 6)When you edit the save game you will find a number like 07 -10
 according to the number you had when you saved the game.ecc change
 the number on the left side to 60 you will have 99 bullets.