On the larger grease guns, there is a small plug on the head to unscrew in order for the air to escape without pulling back the plunger. When you pull back the plunger, it places the head of the gun under negative pressure which is more likely to draw air into a space where you really don't want it.
If there is no bleed screw, try unscrewing the tube under the head. That's a bit of a balancing act between pulling back the plunger far enough to reduce the pressure on the head without sucking air in, or pushing gobs of grease out, in the process.
Either way, there will be some cleanup involved. At work, we filled our guns off of an air powered grease pump system from a 3000 lb bulk tank using a fitting in the bleed screw hole. When the plunger was all the way out, it was full and we shut off the flow. It took only a few seconds and the gun never lost its prime. No cleanup involved either . . . until the end of the shift.
The third option is to use grease in bulk cans and forget the cartridges. Draw back and latch the plunger, unscrew the head, and put the end of the barrel over the can of bulk grease and release the plunger to empty the barrel. Then push the end of the barrel into the bulk grease and pull back the plunger to draw a full load of grease. With a small dome of grease at the end of the barrel, screw the head back on. The excess grease dome pushes out the air as it contacts the head. It works in theory, and most of the time in practice as well.
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Sometimes you get on a roll, sometimes the roll gets on you.
MF GC2310, Husqvarna YTH20B42T
Down for Repairs
MF1655 w/ FEL, MF1655, MF12H, MF8H, MF7H
Spending too much time on MTF to work on my toys.