If the barrels were properly rust blued it is doubtful that the ribs have come loose but to check for looseness support the barrels from the barrel hook and lightly tap or flick the barrels with a finger nail all along the each side of the barrels. If the barrels ring like chimes the ribs are tight, if they produce a dull thud they have or are coming loose. The sound emanating from inside the barrels is most likely caused by a bit of solder which has come loose and is banging about inside the rib or part of teh missing bead. Brownells and Galazan sell replacement press in beads.
