A grease gun loads from the back, not the front

A grease gun holds thick lubricant in a cylinder and pushes it out through a nozzle when you pull the trigger. To load one, you unscrew the barrel from the handle, insert a grease cartridge into the empty barrel, screw the barrel back on, and then prime the gun by pulling the handle until grease reaches the nozzle. The whole process takes about two minutes and works the same way whether you own a manual caulk gun, a pistol-grip grease gun, or a larger drum-fed model.

The confusion usually comes from the nozzle: it looks like the loading end, but it is not. Everything you load goes in through the back of the barrel, and the nozzle only dispenses what is already inside.

Key Takeaways

  • Unscrew the barrel (the long cylinder) from the handle or pump mechanism before you try to insert a cartridge.
  • Grease cartridges come in standard sizes — most common are 14-ounce tubes that fit into the barrel of a pistol-grip gun.
  • After inserting the cartridge, screw the barrel back on hand-tight, then pull the handle or pump several times to push air out and bring grease to the nozzle.
  • If grease does not come out after priming, the cartridge may not have seated properly or the nozzle may be clogged.

Unscrew the barrel from the handle

The barrel is the long metal or plastic tube that holds the grease. On a pistol-grip gun, it screws directly into the handle where the trigger is. On a caulk gun, the barrel slides into a frame and is held by a screw or pin. On a drum-fed gun, the barrel is part of a larger assembly.

For a pistol-grip gun: grip the handle firmly and turn the barrel counterclockwise by hand. It will unscrew after a few turns. You do not need a wrench — hand-tight is enough. If it is stuck, wrap a rag around it for better grip, but do not force it hard enough to crack plastic.

For a caulk gun: locate the screw or pin at the back of the frame that holds the barrel in place. Remove it, then slide the barrel straight out toward you. Some models have a release button instead — press it and the barrel will pop free.

Insert the grease cartridge into the barrel

Grease cartridges are sealed tubes, usually made of plastic or cardboard, with a metal or plastic plunger at one end. The plunger end goes into the gun first. The sealed end with the nozzle fitting stays outside.

Hold the barrel upright with the open end facing up. Slide the cartridge in plunger-end first until it stops. It should sit flush inside the barrel with no gap. If the cartridge is too loose, you have the wrong size — standard pistol-grip guns use 14-ounce cartridges, but some older or specialty models use different sizes.

Once the cartridge is seated, you can screw the barrel back onto the handle or slide it back into the frame, depending on your gun type.

Screw the barrel back on or find it in the frame

For a pistol-grip gun: thread the barrel back onto the handle by turning it clockwise by hand. Tighten it until it is snug but do not over-tighten — you will only have to unscrew it again when the cartridge is empty. Hand-tight is the right amount of pressure.

For a caulk gun: slide the barrel back into the frame until it seats fully, then replace the screw or pin. Make sure the barrel is straight and not tilted, or the plunger will not push evenly and the gun may jam.

Prime the gun by pulling the handle or pump

Priming means pushing out the air that is trapped between the plunger and the grease inside the cartridge. Until you do this, nothing will come out of the nozzle even though the gun is loaded.

On a pistol-grip gun: pull the trigger or handle repeatedly — usually 5 to 10 times — until you see grease start to ooze from the nozzle. The first bit may be thin or watery; that is normal. Keep going until a thick bead of grease appears.

On a caulk gun: pull the handle all the way back, then push it forward. Repeat this motion 5 to 10 times. You will feel resistance increase as the plunger pushes down on the cartridge. Stop when grease reaches the nozzle.

On a drum-fed gun: the priming process is the same — work the pump handle until grease flows. This may take more pulls because the distance is longer.

Attach the nozzle and test the flow

Most grease guns come with a nozzle that screws onto the barrel tip. If your gun did not come with one, you can buy a replacement at any hardware store — they are universal and cost a few dollars. Screw the nozzle on by hand until it is snug.

Before you use the gun on your actual work, test it on a scrap surface or a piece of cardboard. Pull the trigger once or twice to make sure grease flows smoothly. If nothing comes out, the nozzle may be clogged — unscrew it and poke the hole with a thin wire or needle to clear it. If grease still does not flow after priming again, the cartridge may not have seated properly, and you will need to unload and reload it.

What to do if the gun will not prime

If you have pulled the handle 10 or more times and still see no grease at the nozzle, the most common cause is that the cartridge did not seat all the way into the barrel. Unscrew the barrel, check that the cartridge is pushed in as far as it will go, and try again.

The second most common cause is a clogged nozzle. Unscrew the nozzle from the barrel tip and look through it toward a light. If you cannot see through, soak the nozzle in warm water for a few minutes, then use a thin wire to poke out any dried grease. Screw it back on and prime again.

If the cartridge itself is old or has been stored in very cold conditions, the grease inside may be too stiff to flow. Warm the cartridge under warm running water for a minute or two, then try priming again. Do not use hot water or a heat gun — you can damage the cartridge seal.

Frequently Asked Questions

Can I use any grease cartridge in my gun?

No. Pistol-grip guns use 14-ounce cartridges, but caulk guns and specialty models may use different sizes. Check your gun's manual or measure the barrel diameter. Buying the wrong size wastes money and leaves you unable to load the gun. Most hardware stores stock the standard 14-ounce size.

What if grease leaks out around the plunger?

A small amount of seepage is normal when you first load the gun. If grease is pouring out, the cartridge is not seated properly or the barrel threads are damaged. Unload the gun, inspect the cartridge and barrel for cracks, and reload. If leaking continues, the barrel may need replacement.

How do I unload a grease gun?

Unscrew the barrel from the handle, then push the plunger all the way down to force the cartridge out from the bottom. You can then dispose of the empty cartridge. Wipe the inside of the barrel with a dry cloth before loading a new one.

Do I need to prime the gun every time I load it?

Yes. Every new cartridge has air trapped inside, so you must prime before the first use. If you reload the same gun after using it, priming is usually faster the second time because less air is trapped.

Can I store a loaded grease gun for months without using it?

Yes, but the grease may harden slightly, especially in cold storage. Before using it again, work the handle or trigger a few extra times to loosen the grease. If it does not flow after 15 pulls, warm the gun under warm water and try again.