This must be the one your talkin about
:
Sometimes they take a lot of pressure. More than you would think to be safe. Wear eye protection!
They take a lot of force and when they pop they POP!
Also, hitting the side of the arm will help. Don't hit the arm though, place a block of wood over it and hit that.
Also, make sure you screw the nut up to the top and press on that. You don't want to crush the top of the bolt. You'll need to get the allen key in there to torque it back down.
Danny