Long ago in my teenage days, and my first time out with a cap and ball .44 Colt, I learned the importance of proper fitting percussion caps and nipples/cones.
Chain fire! A BIG cloud of smoke, and hand numbing recoil. The ball at the 6 o/clock position jammed into the loading lever. I don't know where the other balls went, but I don't think they followed the same direction as the one that went down the barrel!
Loose caps, and the fire jumped across the back of the cylinder. I never believed the stories of chain fire due to flash jumping the balls at the front of the cylinder, but I do know that loose caps not fitting tightly on the nipples/cones can cause a chain fire.
It sure makes a heck of a short range defense load!
I now will gently file/dress my nipples/cones to fit percussion caps tightly on all my cap and ball revolvers.