Forget the grease gun... where can a person buy a decent chuck? I have half a dozen grease guns, including a JD one and they all work fine but all the chucks are junk. Even the one's with an adjustable chuck are problematic. Either it's too loose and grease just squirts out from around the fitting or they are so tight that they rip out the jerk fitting when you try to remove it.
I am willing to pay most anything to get a decent chuck that stays on tight enough to allow the jerk to accept the grease yet doesn't tear the zerk out of the threads when I remove it.
The only decent chuck I current own is one that my dad used when he was a mechanic. It's one of those right-angle jobbies that rotates. He retired over 10 years ago and the chuck has to be 20 years old and nearly worn completely out. Pathetically it's still the best chuck out of all of them.