A few thoughts... ( been shooting C&B revolvers since Reagan's 2nd term)... cooler heads in the ongoing "chainfire panic" discussions seem to agree that loose caps or caps that fall off may, in fact, be a greater cause for these events than failure to schmear some slime over the top of a loaded chamber or the absence of wads and such.
I've never had a "chainfire". Never heard of one except in panicky threads on the Interwebs. But I've always been very meticulous about how I load and what materials I use. Here's my latest thoughts though, regarding caps falling off and "pinched" caps, etc.
My cherished transition NMA, upon resurrection from Wallhanger Hell, Had original and very rusty nipples. I would load and cap all 6 chambers, and after two rounds fired, two or three caps would have fallen free, sometimes down in the action, needing to be picked out before re-capping and continuing to fire the weapon. I worried, initially, about chainfires occurring because of flashover into an uncapped but loaded chamber. But it never happened. Eventually I got the olf nipples drilled and easy-outed and replaced with Track of the Wolf replacements, but not before I'd fired over 200 rounds on the old rusted nipples.
I ask myself, "why no chainfires, dum-dum?" and here's a possible explanation. When I brought the old pistol back to use, I bought Mark Hubbs rebated bullet mold, cast my own conical bullets and built paper cartridges with Goex FFFg. So there is no loose powder anywhere on my weapon, It seems that indirect sparks from the possible flashover isn't enough to ignite the hemp papers I use. However, a properly capped chamber has failed to fire perhaps three times in about 500 rounds over the last two years. Every occasion, it was after 20 or 30 rounds had already been fired and unburnt paper pieces were the culprit. A simple piercing through the nipple with a pick and a fresh cap and I have ignition. Everytime.
My conclusion is that proper care to not have loose powder stuck in some greasy mess on the front of the cylinder and frame, the persistent use of paper cartridges and real blackpowder are the reasons I have no chainfire/unintended ignition issues AND I get consistent ignition even from old worn parts. Thanks for your indulgence in this long epistle.