You have to open the weapon_equip.ini file there you will find every thing you need about wepons (exept the price which is in the weapons_goods.ini)
search for the missile/weapon you wana change

(note : you have to know the nickname for the weapon or search manualy caus the names there are a *bit* diffrent from the game, don't worry you should be able to find them if you try. i cant give you names right now caus i dont have much time now but i'll see if i can search it for u )

for missile usualy there is several entries:
[motor <--- for controling the missile motor
.....

[explotion <--- here you modifiy the power, damage and the radius of the
... explotion of your weapon

[munition <--- here's were you need to go
...
hit_effect = <--- (or as i can remember since i'm not on my PC)that's the effect
of the hit.
con_effect = <--- (again as far as i remember) that's what you EXACTLY
want,here's the effect of the missile

[gun <--- several main stuff about the munition launcher : fire delay, speed, ....


what you have to do is find the effect u want ( i think it has to start with " no_ " )
and put it were you want.

thanks