I've got a well-used 550 and this problem just cropped up. My primer cup is not picking up a primer. So, I take it apart and clean with alcohol. Still doesn't work. I then notice that the primer bar itself is pretty tightly wedged with the cast part at the bottom of the primer tube. (This cast part is anchored by two Allen head screws which come from the bottom up.) The primer bar does not want to slide; it's like the spring (which forces the bar to slide) is too weak. Any clues?