Load first, burp second
1 of 2
Photo 1. Pack the head
Scoop any remaining grease out of the old cartridge and pack it into the head.
2 of 2
Photo 2. Burp from the top
Unscrew the plug on the head of the gun, but keep it positioned directly over the hole. Screw it back in as soon as the air bubble clears.
Prevent air locks by filling the grease gun head before adding the new cartridge (Photo 1). Insert the new cartridge and screw on the barrel until it seats against the head. Then back it off two turns and release the spring tension. The remaining air should bleed out through the loose threads. Finish tightening the barrel.
If you've done that but still have an air lock, remove the plug (Photo 2).