One thing I've seen at least twice in this thread, that is worth highlighting:

REMOVE THE BORE OIL BEFORE YOU LOAD!!!

Back when I shot only a sidelock, I spent a couple seasons having a few frustrating misfires on game. It was ALL my fault, I did not swab the oil before I loaded with Pyrodex. I learned my lesson, and never had another misfire in the field.

This was also because some well-meaning old-timer on an old ML email list told me to use only Murphy's Oil Soap to clean my ML, and I did....turns out that stuff CAUSES rust and I had to oil the crap out of my barrel to keep it from rusting. I took my lumps and learned from it, no more Murphy's, a fraction the oil, and problem solved.