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Well ted, I think I know of a cure, but not sure that I can type my explanation well enough. As you have already stated, with the loaded rounds in place, the hammer is not able to travel all the way forward enough when you let it down on a live round. If the hammer is not allowed to travel all the way forward, the bolt leg will not be allowed to pop up over the cam lip so that it can be in the correct position to be lowered back down into the frame and free of the cylinder notches when the hammer is once again pulled back. All that is really happening in this case is that the hand is trying to rotate the cylinder when attempting to pull the hammer back, but the bolt is remaining in the cylinder notches and causing the process to lock up.I have had this happen on several percussion cylinders myself with new guns. They would cycle fine until I put a percussion cap on the cones. Even though the caps were fully seated, there no longer remained enough tolerance between the barrel breech face, cylinder face, the cones, and the hammer face when in the forward resting position. The cure is to open up the tolerance somewhere along one of the relationships. For me, the easiest seems always to remove a tiny bit of metal from the hammer face.Before doing that though, you might try shooting it some and see if the hammer face will peen back some from striking the pins in the cylinder. If it will peen, you will most likely then have enough tolerance without filing away any metal. Just load it up with 5 rounds so you can initially let the hammer down on an empty cylinder which will allow the action to fully cycle the first time that you go to cock it in order to fire the first round.Pietta hammers are somewhat soft. The face of the hammer on my 1860 peened back in short order once I got to shooting the gun. It is peened back so far now though that I am looking at either replacing it or drilling out the face an installing a hardened insert.I hope my jumbled words make sense.