Projectiles pushing PhysicsShape (and vector math)

Hi, I'm trying to get the projectiles to push a physics shape. I'm using bullet physics and have applied the fix from this thread here. http://www.garagegames.com/community/forums/viewthread/135749

This is my code: theoretically I'm just applying the force from the projectile direction onto the shape?

function BulletProjectile::onCollision(%this,%obj,%col,%fade,%pos,%normal)
{
   // Apply impact force from the projectile.
   if ( %col.getType() & $TypeMasks::ItemObjectType )
   {
	   %vec = %obj.initialVelocity; //projectile doesn't have a getVelocity() 

	   // Add impulse
	   %col.applyImpulse(%pos, %vec);
	}

   
   // Apply damage to the object all shape base objects
   if ( %col.getType() & $TypeMasks::GameBaseObjectType )
      %col.damage(%obj,%pos,%this.directDamage,"BulletProjectile");
}

It kind of works, but if I shoot the corner it just spins in a random direction. Can someone help?