This category covers the loading end, the carrying hardware and the gun's internal service parts: follower plates and springs, filler pumps and nipples, cartridge tools, holders and brackets, plungers, seals, bleeder valves and repair kits. The parts that carry and discharge grease are listed separately - couplers and dispensing tips under Couplers & Dispensing Tips for Grease Guns, and hoses, pipes and barrels under Hoses, Pipes & Barrels for Grease Guns.

The follower plate sits behind the grease inside the barrel and, pushed by its spring, keeps the charge fed forward to the outlet as the gun empties. A worn, distorted or badly fitting plate lets grease pass around its edge instead of being pushed ahead of it, so the gun loses prime near the end of a charge and traps air. Replace it if it is scored, no longer a close fit in the barrel, or if priming problems appear repeatedly on the last third of a load.

Almost always an air pocket behind the follower, introduced while loading. Continuing to pump compresses the air instead of moving grease and achieves nothing. Open the bleeder valve, push the follower rod in to expel the trapped air, then close it and pump again. If the gun still will not prime, suspect a worn follower plate, a failed plunger seal or a blocked coupler, in that order, rather than a fault with the grease itself.

With a filler pump, which transfers grease from a pail or drum through the gun's filler nipple without exposing either to the air. That matters because dirt entering the barrel during loading is carried straight to a bearing at the next application. Draw the plunger rod back as the barrel fills, then bleed any trapped air before use. Bulk loading is cheaper per kilogram than cartridges and is the normal arrangement where a site runs several guns.

It vents air trapped in the barrel. Air enters during loading, particularly with bulk filling, and once trapped behind or around the follower it compresses under pumping instead of transmitting pressure to the grease, so the gun feels like it is working while delivering nothing. The bleeder valve releases that air in a few seconds. A gun without one, or with a seized one, has to be partially dismantled to achieve the same result.

Yes, and it should be marked so it stays that way. Greases with incompatible thickeners can soften or harden dramatically when mixed, and either outcome destroys the lubricating film faster than under-greasing would. A gun retains a significant amount of its previous product in the barrel, head and hose, so switching product without a full purge contaminates the next application. Colour-coded holders, caps and washers exist specifically to make dedication visible on a busy site.

A spare follower plate and spring, a plunger seal or complete repair kit for the guns in use, and a spare bleeder valve. These are the items that stop a gun working and are cheap relative to replacing it. Keep them by manufacturer and model, since barrel diameters and head threads differ, and hold a filler pump and spare filler nipples where guns are loaded from bulk rather than cartridges.