I have had....
....one chain fire event in my entire life.
It was on a C.O.M. Sheriff's Model 1851 pattern in brass frame.
The pistol was in good condition. I loaded an average load with a nicely fitting ball and grease over the ball (.375). I pinched the cap to get it to remain on the nipple and I think that was my problem.
I know there are those among us who will declare that pinching a cap is done all of the time and it is a safe and accepted practice which does not promote chain fires. But as the bullet fit well and the chambers were aggressively schmutzed I have to believe that the gases came from the aft end of the cylinder. I don't pinch caps any more.
The effect of that event was to loosen the arbor on this otherwise good shooting revolver.
My reading of history convinces me that most bad government results from too much government. Thomas Jefferson