How to Use a Battery Powered Grease Gun? | Battery, Prime, Trigger

A battery powered grease gun works by charging the battery, loading grease, priming out trapped air, then locking the coupler onto a fitting and squeezing the trigger until fresh grease appears.

Skipping the prime turns a two-minute job into a twenty-minute fight. Do that properly and the rest is simple — though your battery platform decides which tool is even an option.

Here is the sequence straight from the manufacturer’s procedures, plus the two mistakes behind most “my grease gun won’t work” complaints.

What You Need Before the First Squeeze

Milwaukee’s cordless grease guns come in two separate battery platforms, and an M12 battery will not fit an M18 tool.

• Battery: the Milwaukee M12 model 2446-20 uses M12 batteries; the M18 model 2646-20 runs on the separate M18 platform.
• Grease: a standard cartridge or bulk grease, depending on how you load it.
• Access: enough room to seat the coupler squarely on the fitting — a crooked seat leaks grease and looks like a tool failure.

That shared platform is the main draw for anyone already invested in the line.

How Do You Load Grease Into a Cordless Grease Gun?

Grease goes in by cartridge or bulk loading; Milwaukee’s manual describes both approaches: suction loading from a bulk container, and pump loading through the head.

Cartridge loading is cleaner for most people: open the barrel, drop in the cartridge, peel the pull tab, reassemble. Suction loading suits high-volume shop use but is messier and easier to get wrong on a first attempt.

Whichever route, fill the barrel completely. A partially filled barrel is a common reason grease never shows up at the fitting, and it masquerades as a priming problem.

Priming the Grease Gun: The Step Everyone Skips

Priming pushes air out of the hose and head so grease can flow. Milwaukee’s documented M18 sequence:

1. Insert the charged battery pack.
2. Push the priming valve until air escapes.
3. Hold the hose assembly by its spring strain relief, pointed away from your body.
4. Pull the trigger for 10–20 seconds until grease appears at the coupler.

That safety instruction is not boilerplate. Grease inside the hose is under pressure, and a hose pointed at a hand or face can deliver it with real force.

If grease still doesn’t appear after 20 seconds, re-prime. On a fresh cartridge, one or two priming cycles usually clears the system.

Attaching the Coupler and Applying Grease

Once grease is flowing, press the coupler straight onto the fitting and squeeze the trigger until fresh grease emerges around the seal — that visible purge is your signal to stop. A couple of trigger pulls is normally enough for a standard fitting.

If the coupler won’t seat, back off and check alignment; a coupler pushed on at an angle won’t lock, and forcing it wears the jaws. If it seats but nothing flows, the tool needs another priming cycle rather than more pressure.

Wiping the fitting before attaching keeps grit out of the joint, and releasing with a slight tilt makes the coupler pop free instead of dribbling grease down your hand. If you’re weighing platforms before buying — M12 for tight spaces versus M18 for volume — comparing the tested options side by side saves second-guessing.

Milwaukee’s grease gun operator manual is the document to keep on hand if a step here doesn’t match your specific model.

For an M12 versus M18 comparison before you commit, our roundup of the best battery powered grease guns breaks down which models suit which jobs.