For this hack you will need:
1 PS3
1 Call Of Duty 4
1 Usb memory stick
1 computer or laptop
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Step 1: Plug your usb memory stick into ps3.

Step 2: Go to saved game data find the call of duty game save press tringle while on it press copy and select he usb memory stick

Step 3: Plug your usb into the p.c or laptop

Step 4: Go to my computer and open you your usb file then click ps3 then savedata then Bles(there will be a few numbers here)

Step 5: Right click on GPADO_SP and open it with notebook

Step 6: Copy and paste This in to GPADO_SP , dont take anything out just paste it at the end:
set melee "9"
set player_meleeRange "99999"

Step 7:Save this dont click save as, just save or ctrl + S safley remove the hardware.

Step 8: Plug usb into ps3

Step 9: Go to saved game data, click on the usb (triangle), now go to the call of duty save and paste it

Step 10: it will say it will overwrite old data, click yes and your done!

THIS WILL ONLY WORK IN SINGLE PLAYER, AND FOR IT TO WORK YOU HAVE TO HAVE YOUR CROSSHAIRS AIMING ON THE TARGET, WIL NOT WORK SPLITSCREEN