No, you cannot use any nozzle to reduce the size of the opening on the HJ5000 Heat Gun. Using a nozzle or other device that reduces the size of the opening will restrict the airflow from the product, causing heat to build up inside the heater assembly. This will cause damage to the product and will likely cause the heater to fail.
If you are looking to reduce the opening on the HJ5000 Heat Gun for soldering or rework, we recommend the use of the Hakko FR-801 SMD Hot Air Rework Station as it provides a much more controlled level and focus of hot air which is needed to preven damage to circuit boards and components.