The current Lee hand prime is problematic. I think there have been three versions since the 1960's. I have the "first version" which has a round primer tray and used cheap zinc materials for the priming arm and hand prime body. I broke all sorts of priming arms and the top would lift off on the hand prime body, but, it is the version I prefer. Lee must have had primer explosions in their hand tool, because the second version used the same body and priming arm, but the tray was redesigned. It became square and it had a blast cage. Primers are lifted up through the blast cage, above the main mass of primers. The cage broke on mine and so did the plastic retainers that held the top to the bottom. It also was relatively unreliable in feed. The current version has a very complicated clear plastic primer feed mechanism. It is obviously much more intensively designed to prevent primer explosion propagation to the tray. There are a lot of moving parts and springs, which block any blast from the primer tray, but, as Scottie said "the more complicated the plumbing, the easier it is to plug up the drain". My Lee hand prime tool sticks and primers jam up frequently within the mechanism. I am consistently disassembling the thing to clear jams. And it is getting worse the more I use the thing. The hand prime tool body and lever arm appear to be more robust.