If your goal is purely to stop the grenade once it hits an object, use the code below. This adds an eventHandler to the projectile which sets its velocity to [0,0,0] once it "explodes" (explodes on hit). Simply populate the array with all the class names for your ammo. This method foregoes modifying any config files and can be applied to any mod, so long as you have the class names. As I have many other effects applied to projectiles, I placed this in my initPlayerLocal.sqf script.
addMissionEventHandler ["ProjectileCreated", {
params ["_projectile"];
_projectile addEventHandler ["Explode", {
params ["_projectile", "_pos", "_velocity"];
if (typeOf _projectile in ["rhs_40mm_m713_red","rhs_40mm_m714_white","rhs_40mm_m715_green","rhs_40mm_m716_yellow"]) then {_projectile setVelocity [0,0,0]};
}];
}];