Priming a lever-action grease gun is a process that ensures the gun is ready to dispense grease efficiently and without any air pockets that could interfere with the lubrication process. Here's a step-by-step guide on how to prime a lever-action grease gun:

1. **Clean the Barrel:**
- Before you start, make sure the barrel of the grease gun is clean. Any old or hardened grease can prevent the new grease from being loaded properly.

2. **Attach the Cartridge:**
- Insert a new grease cartridge into the gun. Make sure it's seated correctly according to the manufacturer's instructions.

3. **Remove the Safety:**
- If your grease gun has a safety mechanism, make sure to disengage it.

4. **Pump the Lever:**
- With the gun pointed in a safe direction, start pumping the lever. This action draws air into the chamber.

5. **Load the Plunger:**
- Once you have the cartridge in place and the lever is pumped a few times, you'll need to load the plunger. This is usually done by pumping the lever until you feel resistance, indicating that the plunger is at the end of its stroke.

6. **Prime with Grease:**
- With the plunger loaded, continue to pump the lever. The first few pumps will force a small amount of grease into the barrel, which is necessary to displace the air and prime the gun.

7. **Check for Air:**
- After priming, you may need to check for air. If you see air bubbles coming out of the gun's nozzle or if the grease is not coming out smoothly, you may need to continue pumping until the air is fully expelled.

8. **Apply Pressure:**
- Once you're sure the Portable Grease Gun gun is primed and there's no air left, you can apply pressure to the grease cartridge by continuing to pump the lever. This will force the grease down the barrel and out the nozzle.

9. **Attach the Nozzle:**
- Screw on the appropriate nozzle for your application. Make sure it's tightened securely.

10. **Test the Gun:**
- Before using the grease gun on your equipment, test it on a scrap piece of metal or another non-critical surface to ensure it's working properly.

11. **Safety:**
- Always keep the safety on when not in use and follow all safety protocols when operating a grease gun.

Remember, the specific steps and features may vary slightly depending on the make and model of your grease gun, so it's always a good idea to consult the user manual for your specific tool. Proper priming is crucial to ensure the grease gun operates efficiently and to prevent damage to the equipment you're lubricating.