Yes I'm using a 550. And I notice that the problem was on the two screws that hold the powder funel/system to the powder die. That litle piecs was inverted and the guide did not went all the way, so after some strokes the powder system moved up the powder dy and the system could not activate the powder bar completely. I disasembly the powder system and put the pieces in the correct way with the guide pointing down, tighten the screws (I saw the difference) and now the powder system is right in place and tight.