Object instantiate, Projectile problems

I’m having problems with projectiles, On this demo {{title}} when you fire a missile they come out spinning most of the time, not static in the direction they where fired from. Also lots of the time when you leave the starting rotation, they come out going random directions.

The code that creates them:

Transform trfrm = firePoints[gun].transform;
GameObject clone = (GameObject)Instantiate(projectile, trfrm.position, trfrm.rotation);	
clone.rigidbody.AddForce(clone.transform.up * projectileSpeed);

this is one of the firePoints, The other is exactly the same on the right (they are children of the helicopter):

Your projectile may be colliding with something else when it’s created. Use Physics.IgnoreCollision

It seems that the projectile is being created inside or touching some collider: this applies a repulse force to the rigidbody that makes it spin crazily, and possibly fly to weird directions. If that’s the case, move the object referenced by firePoints[gun] ahead enough to ensure that the projectile won’t touch any collider (by the way, the fire point object should not have a collider: if any, remove it).