Nope… I did not tried it…
Thanks for trying to help! 
Thanks @yaustar It worked! 
I did same…
Placed empty entity right above and below main weapon…
var BalancerVal = new pc.Vec3().sub2(this.topBalancer.getPosition(), this.bottomBalancer.getPosition());
this.mainWeaponHolderPoint.lookAt(this.weaponAxisLockPoint.getPosition(), BalancerVal);
Thank you very much! 