hi guys
if you want replacment your gun to new sound in cod4 

all you need
go to
\Activision\Call of Duty 4 - Modern Warfare\zone\english

and copy file and replace

to another map to work fine

just change name file and replace

example:

mp_backlot_load
mp_bloc_load
mp_bog_load
mp_broadcast_load
>>
...

*(work online/lan) :D


enjoy :)