Instantiate a Prefab as child

Hello, I try to Instantiate a Weapon as an Child of a Empty Gameobject which is in Position with the Right Hand of my Model ,it works well but the Position of the Weapons are not correct ... GameObject w = Instantiate(ca.WeaponMesh[_weaponIndex],_pc.WeaponMount.transform.position,_pc.WeaponMount.transform.rotation)as GameObject; w.transform.parent = _pc.WeaponMount.transform; What i doinig wrong ???