I have a dozen or so C&B revolvers, all repros, some of about all kinds. never had a chainfire in well over 40 years, and never seen one. I only put grease on top of the balls for a VERY brief MESSY period. an old timer (at the time, now I am) told me grease on the balls was silly and messy, he further said he learned to use "paste board" cut into over sized disks soaked in beeswax between the powder and ball, not to prevent chainfires, but to help keep the barrel and cylinder from fouling as much. he also told me that when using new nipples to dryfire them a few times to make the caps fit tighter, not to prevent chainfires, but to keep the caps from backing off and preventing the revolver from cocking. more sound advice was when cocking Colt pattern revolvers to point the barrel up to prevent spent caps from falling into the "lock works". his advice paid off, and after cases of BP trough these revolvers, no problems. I do maintain my revolvers, ensure the barrel wedge is tight and the cylinder gap is VERY small. I don't know why some people have chainfires, maybe the same reason some people dry ball, not paying attention. I am getting older, and perhaps some of these things may start happening to me.