thats cause the sound is tied to the fire effect.
copy the fire/effect value and search for that value in the particles.dat file, it should point to a node such as "$Gun_muzzle_flash".
Now delete all particle generators from that node and the smoke should be gone, while still having sound
Veel geluk met het wegkrijgen van de rook, t zou moeten lukken nu
BTW, just curious: why do you want to get rid of the smoke?